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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Feb. 22, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	ANSS
Entity Registrant Name	ANSYS INC
Entity Central Index Key	0001013462
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		83,771,828
Entity Well-Known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 11,318,000,000

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 777,139	$ 881,501
Short-term investments	225	286
Accounts receivable, less allowance for doubtful accounts of $8,000 and $6,800, respectively	317,700	124,659
Other receivables and current assets	216,113	263,820
Total current assets	1,311,177	1,270,266
Property and equipment, net	61,655	57,096
Goodwill	1,572,455	1,378,553
Other intangible assets, net	211,272	157,625
Other long-term assets	82,775	35,972
Deferred income taxes	26,630	42,111
Total assets	3,265,964	2,941,623
Current liabilities:
Accounts payable	7,953	6,042
Accrued bonuses and commissions	79,945	69,925
Accrued income taxes	8,726	5,760
Other accrued expenses and liabilities	99,559	86,335
Deferred revenue	328,584	440,491
Total current liabilities	524,767	608,553
Long-term liabilities:
Deferred income taxes	30,077	1,461
Other long-term liabilities	61,573	85,778
Total long-term liabilities	91,650	87,239
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $.01 par value; 2,000,000 shares authorized; zero shares issued or outstanding	0	0
Common stock, $.01 par value; 300,000,000 shares authorized; 93,236,023 shares issued	932	932
Additional paid-in capital	867,462	873,357
Retained earnings	2,919,411	2,316,916
Treasury stock, at cost: 9,601,670 and 9,044,498 shares, respectively	(1,075,879)	(907,530)
Accumulated other comprehensive loss	(62,379)	(37,844)
Total stockholders’ equity	2,649,547	2,245,831
Total liabilities and stockholders’ equity	$ 3,265,964	$ 2,941,623

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts		$ 6,800
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	93,236,023	93,236,023
Treasury stock, shares	9,601,670	9,044,498

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue:
Total revenue	$ 1,293,636	$ 1,095,250	$ 988,465
Cost of sales:
Amortization	27,034	36,794	38,092
Total cost of sales	155,885	150,164	146,860
Gross profit	1,137,751	945,086	841,605
Operating expenses:
Selling, general and administrative	413,580	338,640	269,515
Research and development	233,802	202,746	183,093
Amortization	13,795	12,972	12,755
Total operating expenses	661,177	554,358	465,363
Operating income	476,574	390,728	376,242
Interest income	11,419	6,962	4,209
Other expense, net	(908)	(1,996)	(136)
Income before income tax provision	487,085	395,694	380,315
Income tax provision	67,710	136,443	114,679
Net income	$ 419,375	$ 259,251	$ 265,636
Earnings per share – basic:
Earnings per share	$ 4.99	$ 3.05	$ 3.05
Weighted average shares	83,973	84,988	87,227
Earnings per share – diluted:
Earnings per share	$ 4.88	$ 2.98	$ 2.99
Weighted average shares	85,913	86,854	88,969
Software licenses
Revenue:
Total revenue	$ 576,717	$ 624,964	$ 568,174
Cost of sales:
Total cost of sales	18,619	34,421	28,860
Maintenance and service
Revenue:
Total revenue	716,919	470,286	420,291
Cost of sales:
Total cost of sales	$ 110,232	$ 78,949	$ 79,908

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 419,375	$ 259,251	$ 265,636
Other comprehensive (loss) income:
Foreign currency translation adjustments	(24,535)	19,808	(5,488)
Comprehensive income	$ 394,840	$ 279,059	$ 260,148

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 419,375	$ 259,251	$ 265,636
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	59,255	67,678	69,587
Deferred income tax benefit	(33,675)	(2,693)	(10,921)
Provision for bad debts	1,577	1,474	2,009
Stock-based compensation expense	83,346	53,154	33,347
Other	410	21	1,290
Changes in operating assets and liabilities:
Accounts receivable	(74,455)	(14,406)	(17,388)
Other receivables and current assets	(30,241)	(18,498)	(39,644)
Other long-term assets	3,288	2,343	(7,167)
Accounts payable, accrued expenses and current liabilities	19,920	27,045	16,919
Accrued income taxes	1,086	1,215	9,052
Deferred revenue	56,213	20,648	41,430
Other long-term liabilities	(19,662)	33,206	1,830
Net cash provided by operating activities	486,437	430,438	365,980
Cash flows from investing activities:
Acquisitions, net of cash acquired	(283,026)	(63,885)	(7,891)
Capital expenditures	(21,762)	(19,149)	(12,443)
Other investing activities	(8,892)	(14,409)	(11,839)
Net cash used in investing activities	(313,680)	(97,443)	(32,173)
Cash flows from financing activities:
Purchase of treasury stock	(269,801)	(336,042)	(336,335)
Restricted stock withholding taxes paid in lieu of issued shares	(28,879)	(11,112)	(5,057)
Contingent consideration payments	0	0	(1,048)
Proceeds from shares issued for stock-based compensation	41,019	52,503	53,811
Other financing activities	(5,014)	0	(1)
Net cash used in financing activities	(262,675)	(294,651)	(288,630)
Effect of exchange rate fluctuations on cash and cash equivalents	(14,444)	20,678	(6,866)
Net (decrease) increase in cash and cash equivalents	(104,362)	59,022	38,311
Cash and cash equivalents, beginning of period	881,501	822,479	784,168
Cash and cash equivalents, end of period	777,139	881,501	822,479
Supplemental disclosures of cash flow information:
Income taxes paid	$ 87,244	$ 116,389	$ 118,455

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive (Loss)/Income
Beginning balance at Dec. 31, 2015	$ 2,194,427	$ 932	$ 894,469	$ 1,792,029	$ (440,839)	$ (52,164)
Beginning balance, shares at Dec. 31, 2015		93,236			5,097
Treasury shares acquired	$ (336,335)				$ (336,335)
Treasury shares acquired, shares	3,700				3,700
Stock-based compensation activity, including tax benefit	$ 90,165		(11,459)		$ 101,624
Stock-based compensation activity, including tax benefit, shares					(1,249)
Other comprehensive (loss)/income	(5,488)					(5,488)
Net income for the year	265,636			265,636
Ending balance at Dec. 31, 2016	2,208,405	$ 932	883,010	2,057,665	$ (675,550)	(57,652)
Ending balance, shares at Dec. 31, 2016		93,236			7,548
Treasury shares acquired	$ (336,042)				$ (336,042)
Treasury shares acquired, shares	2,750				2,750
Stock-based compensation activity, including tax benefit	$ 94,409		(9,653)		$ 104,062
Stock-based compensation activity, including tax benefit, shares					(1,254)
Other comprehensive (loss)/income	19,808					19,808
Net income for the year	259,251			259,251
Ending balance at Dec. 31, 2017	2,245,831	$ 932	873,357	2,316,916	$ (907,530)	(37,844)
Ending balance, shares at Dec. 31, 2017		93,236			9,044
Cumulative effect of the ASC 606 adoption	183,120			183,120
Treasury shares acquired	$ (269,801)				$ (269,801)
Treasury shares acquired, shares	1,674				1,674
Stock-based compensation activity, including tax benefit	$ 95,557		(5,895)		$ 101,452
Stock-based compensation activity, including tax benefit, shares					(1,116)
Other comprehensive (loss)/income	(24,535)					(24,535)
Net income for the year	419,375
Ending balance at Dec. 31, 2018	$ 2,649,547	$ 932	$ 867,462	$ 2,919,411	$ (1,075,879)	$ (62,379)
Ending balance, shares at Dec. 31, 2018		93,236			9,602

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (PARENTHETICAL) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Stock-based compensation activity, tax benefit	$ 0	$ 0	$ 8,065

Organization	12 Months Ended
Organization	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization ANSYS, Inc. (hereafter the Company or ANSYS) develops and globally markets engineering simulation software and services widely used by engineers, designers, researchers and students across a broad spectrum of industries and academia, including aerospace and defense, automotive, electronics, semiconductors, energy, materials and chemical processing, turbomachinery, consumer products, healthcare, and sports. As defined by the accounting guidance for segment reporting, the Company operates as one segment. Given the integrated approach to the multi-discipline problem-solving needs of the Company's customers, a single sale of software may contain components from multiple product areas and include combined technologies. The Company also has a multi-year product and integration strategy that will result in new, combined products or changes to the historical product offerings. As a result, it is impracticable for the Company to provide accurate historical or current reporting among its various product lines.

Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Accounting Policies

Accounting Principles

The financial statements and accompanying notes are prepared in accordance with accounting principles generally accepted in the United States. Certain items in the notes to the consolidated financial statements of prior years have been reclassified to conform to the current year's presentation. These reclassifications had no effect on reported net income, comprehensive income, cash flows, total assets or total liabilities and stockholders' equity.

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated.

Recently Adopted Accounting Guidance

Revenue from contracts with customers: In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (ASU 2014-09). The Company adopted ASU 2014-09 and its related amendments (collectively known as ASC 606) effective January 1, 2018 using the modified retrospective approach. See Note 3 for the required disclosures related to the impact of adopting this standard.

Income taxes: In October 2016, the FASB issued Accounting Standards Update No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (ASU 2016-16). The Company adopted ASU 2016-16 effective January 1, 2018 using the modified retrospective approach. Previous guidance required the tax effects from intra-entity asset transfers to be deferred until the asset was sold to a third party or recovered through use. ASU 2016-16 eliminated this deferral for all intra-entity asset transfers other than inventory. The adoption of the standard did not have a material effect on the Company’s consolidated financial statements.

Business combinations: In January 2017, the FASB issued Accounting Standards Update No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business (ASU 2017-01). The Company prospectively adopted ASU 2017-01 effective January 1, 2018. This standard narrows the definition of a business. If substantially all the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets, the acquiree is not a business. The standard also requires a business to include an input and a substantive process that significantly contributes to the ability to create outputs. This definition is expected to reduce the number of acquisitions accounted for as business combinations, which will impact the accounting treatment of certain items, including the accounting treatment of contingent consideration and transaction expenses.

Accounting Guidance Issued and Not Yet Adopted

Leases: In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) (ASU 2016-02). ASU 2016-02 requires virtually all leases, other than leases that meet the definition of a short-term lease or leases of intangible assets, to be recorded on the balance sheet with a right-of-use asset and a corresponding lease liability. Leases will be classified as either operating or finance leases based on certain criteria. This classification will determine the timing and presentation of expenses on the income statement, as well as the presentation of related cash flows. The standard is effective for the Company on January 1, 2019. A modified retrospective transition is required upon adoption.

The Company will elect the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allows the Company to carry forward the historical lease classification. In addition, the Company will elect the accounting policy to combine the lease and nonlease components as a single component. The Company will make the accounting policy election to record short-term leases on the consolidated balance sheet.

The Company will primarily have operating leases. The Company expects adoption of the new standard will result in the recognition of a right-of-use asset, and a corresponding lease liability, of $80.0 million - $100.0 million on the Company's consolidated balance sheet. Where applicable, a corresponding deferred tax asset and liability will be recorded related to the right-of-use asset and lease liability. The new standard is not expected to materially impact the Company's consolidated statements of income or consolidated statements of cash flows.

Credit losses: In June 2016, the FASB issued Accounting Standards Update No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13). The current guidance requires the allowance for doubtful accounts to be estimated based on an incurred loss model, which considers past and current conditions. ASU 2016-13 requires companies to use an expected loss model that also considers reasonable and supportable forecasts of future conditions. ASU 2016-13 is effective for annual periods beginning after December 15, 2019, including interim periods within that reporting period. Early adoption is permitted for annual periods beginning after December 15, 2018, including interim periods within that reporting period. The standard requires a cumulative-effect adjustment to the balance sheet as of the beginning of the first reporting period in which the guidance is effective. The Company will not early adopt the standard. The Company is currently evaluating the effect that this update will have on its financial results upon adoption.

Implementation cost accounting for cloud computing arrangements: In August 2018, the FASB issued Accounting Standards Update No. 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (ASU 2018-15). The standard aligns the accounting for costs incurred to implement a cloud computing arrangement (CCA) that is a service arrangement with the guidance on capitalizing costs associated with developing or obtaining internal-use software. Under ASU 2018-15, an entity would apply Subtopic 350-40 to determine which implementation costs related to a CCA that is a service contract should be capitalized. The standard does not change the accounting for the service component of a CCA. The associated cash flows will be reflected within operating activities. ASU 2018-15 is effective for annual periods beginning after December 15, 2019, including interim periods within that reporting period. Early adoption is permitted, including adoption in any interim period for which financial statements have not been issued. Entities can choose to adopt the new guidance (1) prospectively to eligible costs incurred on or after the date the guidance is first applied or (2) retrospectively. The Company is currently evaluating the effect that this update will have on its financial results upon adoption.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements. Estimates also affect the amounts of revenue and expenses during the reported periods. Significant estimates included in these consolidated financial statements include:


•	Allowances for doubtful accounts receivable


•	Income tax accruals, including those related to the Tax Cuts and Jobs Act


•	Uncertain tax positions


•	Tax valuation reserves


•	Fair value of stock-based compensation and probabilities of performance award attainment


•	Contract revenue


•	Acquired deferred revenue


•	Useful lives for depreciation and amortization


•	Valuations of goodwill and other intangible assets


•	Deferred compensation


•	Loss contingencies

Actual results could differ from these estimates. Changes in estimates are recorded in the results of operations in the period that the changes occur.

Revenue Recognition

The Company's revenue is derived principally from the licensing of computer software products and from related maintenance contracts. The Company adopted ASC 606 on January 1, 2018. ASC 606 requires an entity to evaluate revenue recognition by identifying a contract with a customer, identifying the performance obligations in the contract, determining the transaction price, allocating the transaction price to the performance obligations in the contract, and recognizing revenue when (or as) the entity satisfies a performance obligation.

Revenue Recognition Policy 2018 (ASC 606)

The Company enters into contracts that include combinations of products, maintenance and services, which are accounted for as separate performance obligations with differing revenue recognition patterns.

Revenue from perpetual licenses is classified as software license revenue. Software license revenue is recognized up front upon delivery of the licensed product and/or the utility that enables the customer to access authorization keys, provided that a signed contract has been received. Typically, the Company’s perpetual licenses are sold with post-contract support (PCS), which includes unspecified technical enhancements and customer support. The Company allocates value in bundled perpetual and PCS arrangements based on the standalone selling prices of the perpetual license and PCS. Revenue from PCS is classified as maintenance revenue and is recognized ratably over the term of the contract, as the Company satisfies the PCS performance obligation over time.

In addition to perpetual licenses, the Company sells time-based lease licenses. Lease licenses are sold only as a bundled arrangement that includes the rights to a term software license and PCS. Utilizing observable inputs, the Company determined that 50% of the estimated standalone selling price of the lease license is attributable to the term license and 50% is attributable to the PCS. Consistent with the perpetual sales, the license component is classified as software license revenue and recognized as revenue up front at the commencement of the lease. The PCS is classified as maintenance revenue and is recognized ratably over the term of the contract, as the Company provides the PCS benefit over time.

Revenue from training, support and other services is recognized as the services are performed. For contracts in which the service consists of a single performance obligation, such as providing a training class to a customer, the Company recognizes revenue upon completion of the performance obligation. For service contracts that are longer in duration and often include multiple performance obligations (for example, both training and consulting), the Company measures the progress toward completion of the obligations and recognizes revenue accordingly. In measuring progress towards the completion of performance obligations, the Company typically utilizes output-based estimates for services with contractual billing arrangements that are not based on time and materials, and estimates output based on the total tasks completed as compared to the total tasks required for each work contract. Input-based estimates are utilized for services that involve general consultations with contractual billing arrangements based on time and materials, utilizing direct labor as the input measure.

The Company also executes arrangements through independent channel partners in which the channel partners are authorized to market and distribute the Company's software products to end users of the Company's products and services in specified territories. In sales facilitated by channel partners, the channel partner bears the risk of collection from the end-user customer. The Company recognizes revenue from transactions with channel partners at a point in time or over time as appropriate when the channel partner submits a purchase commitment, collectability from the channel partner is probable, a license agreement signed by the end-user customer is received and the performance obligation was met. Revenue from channel partner transactions is the amount remitted to the Company by the channel partners. This amount includes a fee for PCS that is compensation for providing technical enhancements and the second level of technical support to the end user, which is recognized over the period that PCS is to be provided. The Company does not offer right of return, product rotation or price protection to any of its channel partners.

Non-income related taxes collected from customers and remitted to governmental authorities are recorded on the consolidated balance sheet as accounts receivable and accrued expenses. The collection and payment of these amounts are reported on a net basis in the consolidated statements of income and do not impact reported revenues or expenses.

The Company warrants to its customers that its software will perform substantially as specified in the Company's current user manuals. The Company has not experienced significant claims related to software warranties beyond the scope of maintenance support, which the Company is already obligated to provide. The warranty is not sold, and cannot be purchased, separately. The warranty does not provide any type of additional service to the customer or performance obligation for the Company.

The Company's agreements with its customers generally require it to indemnify the customer against claims that the Company's software infringes third-party patent, copyright, trademark or other proprietary rights. Such indemnification obligations are generally limited in a variety of industry-standard respects, including the Company's right to replace an infringing product. As of December 31, 2018, the Company had not experienced any losses related to these indemnification obligations and no claims with respect thereto were outstanding. The Company does not expect significant claims related to these indemnification obligations, and, consequently, the Company has not established any related reserves.

Significant Judgments (ASC 606)

The Company’s contracts with customers typically include promises to transfer licenses and services to a customer. Judgment is required to determine if the promises are separate performance obligations, and if so, to allocate the transaction price to each performance obligation. The Company uses the estimated standalone selling price method to allocate the transaction price for items that are not sold separately, particularly lease licenses sold with PCS. The estimated standalone selling price is determined using all information reasonably available to the Company, including market conditions and other observable inputs. The corresponding revenues are recognized as the related performance obligations are satisfied.

The Company applies a practical expedient to expense sales commissions as incurred when the amortization period would have been one year or less. Sales commissions associated with the initial year of multi-year contracts are expensed as incurred due to their immateriality. Sales commissions associated with multi-year contracts beyond the initial year are subject to an employee service requirement and are expensed as incurred as they are not considered incremental costs to obtain a contract.

The Company is required to adjust promised amounts of consideration for the effects of the time value of money if the timing of the payments provides the customer or the Company with a significant financing benefit. The Company considers various factors in assessing whether a financing component exists, including the duration of the contract, market interest rates and the timing of payments. The Company’s contracts do not include a significant financing component requiring adjustment to the transaction price.

Revenue Recognition Policy 2017 and 2016 (ASC 605)

Revenue from perpetual licenses was classified as license revenue and was recognized upon delivery of the licensed product and/or the utility that enabled the customer to access authorization keys, provided that acceptance had occurred and a signed contractual obligation was received, the price was fixed and determinable, and collectibility of the receivable was probable. The Company determined the fair value of PCS sold together with perpetual licenses based on the rate charged for PCS when sold separately. Revenue from PCS contracts was classified as maintenance and service revenue and was recognized ratably over the term of the contract.

Revenue for software lease licenses was classified as license revenue and was recognized over the period of the lease contract. Typically, the Company's software leases include PCS which, due to the short term (principally one year or less) of the Company's software lease licenses, could not be separated from lease revenue for accounting purposes. As a result, both the lease licenses and PCS were recognized ratably over the lease period. The Company included the revenue for the entire lease arrangement within software license revenue in the consolidated statements of income.

Many of the Company's semiconductor products were typically licensed via longer term leases of 24–36 months. The Company recognized revenue for these licenses over the term of the lease contract. Because the Company did not have vendor-specific objective evidence of the fair value of these leases, the Company also recognized revenue from perpetual licenses over the term of the lease contract during the infrequent occurrence of these licenses being sold with semiconductor leases in multiple-element arrangements.

Revenue from training, support and other services was recognized as the services were performed. The Company applied the specific performance method to contracts in which the service consisted of a single act, such as providing a training class to a customer, and the proportional performance method to other service contracts that were longer in duration and often included multiple acts (for example, both training and consulting). In applying the proportional performance method, the Company typically utilized output-based estimates for services with contractual billing arrangements that were not based on time and materials, and estimated output based on the total tasks completed as compared to the total tasks required for each work contract. Input-based estimates were utilized for services that involved general consultations with contractual billing arrangements based on time and materials, utilizing direct labor as the input measure.

The accounting treatment under ASC 605 associated with arrangements through independent channel partners, non-income related taxes, warranties and indemnification obligations is consistent with ASC 606 described above.

Cash and Cash Equivalents

Cash and cash equivalents consist primarily of highly liquid investments such as deposits held at major banks and money market funds. Cash equivalents are carried at cost, which approximates fair value. The Company's cash and cash equivalents balances comprise the following:



	December 31, 2018			December 31, 2017
(in thousands, except percentages)	Amount		% of Total	Amount		% of Total
Cash accounts	$	331,084	42.6	$	568,587	64.5
Money market funds	446,055		57.4	312,914		35.5
Total	$	777,139		$	881,501

The Company's money market fund balances are held in various funds of a single issuer.

Property and Equipment

Property and equipment is stated at cost. Depreciation is computed using the straight-line method over the estimated useful lives of the various classes of assets, which range from one to forty years. Repairs and maintenance are charged to expense as incurred. Gains or losses from the sale or retirement of property and equipment are included in operating income.

Research and Development

Research and development costs, other than certain capitalized software development costs, are expensed as incurred. Internally developed software costs required to be capitalized as defined by the accounting guidance are not material to the Company's consolidated financial statements.

Business Combinations

When the Company consummates an acquisition, the assets acquired and the liabilities assumed are recognized separately from goodwill at their acquisition date fair values. Goodwill as of the acquisition date is measured as the excess of the fair value of consideration transferred over the net of the acquisition date fair values of the assets acquired and the liabilities assumed. While best estimates and assumptions are used to accurately value assets acquired and liabilities assumed at the acquisition date as well as contingent consideration, where applicable, the Company's estimates are inherently uncertain and subject to refinement. As a result, during the measurement period, which may be up to one year from the acquisition date, the Company records adjustments to the assets acquired and liabilities assumed with the corresponding offset to goodwill as the Company obtains new information about facts and circumstances that existed as of the acquisition date that, if known, would have affected the measurement of the amounts recognized as of that date. Upon the earlier of the conclusion of the measurement period or final determination of the values of assets acquired or liabilities assumed, any subsequent adjustments are recorded in the consolidated statements of income.

Goodwill and Other Intangible Assets

Goodwill represents the excess of the consideration transferred over the fair value of net identifiable assets acquired. Other intangible assets consist of trade names, customer lists, contract backlog and acquired software and technology. Intangible assets that are not considered to have an indefinite useful life are amortized over their useful lives, which are generally two to fifteen years. Amortization expense for intangible assets was $40.8 million, $49.8 million and $50.8 million for the years ended December 31, 2018, 2017 and 2016, respectively.

The Company tests goodwill and indefinite-lived intangible assets for impairment at least annually by performing a quantitative assessment of whether the fair value of each reporting unit or asset exceeds its carrying amount. The Company has one reporting unit. Goodwill is tested at this reporting unit level and indefinite-lived intangible assets are tested at the individual asset level. This requires the Company to assess and make judgments regarding a variety of factors which impact the fair value of the reporting unit or asset being tested, including business plans, anticipated future cash flows, economic projections and other market data.

The Company performs its annual impairment tests for goodwill and indefinite-lived intangible assets as of January 1 of each year unless there is an indicator that would require a test during the year. The Company periodically reviews the carrying value of other intangible assets and will recognize impairments when events or circumstances indicate that such assets may be impaired.

Concentrations of Credit Risk

The Company has a concentration of credit risk with respect to revenue and trade receivables due to the use of certain significant channel partners to market and sell the Company's products. The Company performs periodic credit evaluations of its customers' financial condition and generally does not require collateral. The following table outlines concentrations of risk with respect to the Company's revenue:



	Year Ended December 31,
(as a % of revenue)	2018		2017		2016
Revenue from channel partners	22	%	25	%	24	%
Largest channel partner	4	%	5	%	5	%
2^nd largest channel partner	2	%	2	%	2	%

No single customer accounted for more than 5% of the Company's revenue in 2018, 2017 or 2016.

In addition to the concentration of credit risk with respect to trade receivables, the Company's cash and cash equivalents are also exposed to concentration of credit risk. The Company's cash and cash equivalent accounts are insured through various public and private bank deposit insurance programs, foreign and domestic; however, a significant portion of the Company's funds are not insured. The following table outlines concentrations of risk with respect to the Company's cash and cash equivalents:



	As of December 31,
(in thousands)	2018		2017
Cash and cash equivalents held domestically	$	616,249	$	561,417
Cash and cash equivalents held by foreign subsidiaries	160,890		320,084
Cash and cash equivalents held in excess of deposit insurance, foreign and domestic	754,163		852,138
Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic	452,166		328,902

Allowance for Doubtful Accounts

The Company makes judgments as to its ability to collect outstanding receivables and provides allowances for a portion of receivables when collection becomes doubtful. Provisions are made based upon a specific review of all significant outstanding invoices from both value and delinquency perspectives. For those invoices not specifically reviewed, provisions are estimated at differing rates based upon the age of the receivable and the geographic area of origin. In determining these percentages, the Company considers its historical collection experience and current economic trends in the customer's industry and geographic region. The Company recorded provisions for bad debts of $1.6 million, $1.5 million and $2.0 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Income Taxes

The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period of the enactment date.

The Company records net deferred tax assets to the extent it believes these assets will more likely than not be realized. In making such determination, the Company considers all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax planning strategies and recent financial operations. In the event the Company determines that it will be able to realize deferred tax assets for which a valuation allowance was used to reduce their carrying value, the adjustment to the valuation allowance will be recorded as a reduction to the provision for income taxes.

Tax benefits related to uncertain tax positions taken or expected to be taken on a tax return are recorded when such benefits meet a more-likely-than-not threshold. Otherwise, these tax benefits are recorded when a tax position has been effectively settled, which means that the statute of limitations has expired or the appropriate taxing authority has completed its examination even though the statute of limitations remains open. The Company recognizes interest and penalties related to income taxes within the income tax expense line in the consolidated statements of income. Accrued interest and penalties are included within the related tax liability line in the consolidated balance sheets.

Foreign Currencies

Certain of the Company's sales and intercompany transactions are denominated in foreign currencies. These transactions are translated to the functional currency at the exchange rate on the transaction date. Assets and liabilities denominated in a currency other than the Company's or subsidiary's functional currency are translated at the effective exchange rate on the balance sheet date. Gains and losses resulting from foreign exchange transactions are included in other expense, net. The Company recorded net foreign exchange losses of $3.1 million and $1.9 million for the years ended December 31, 2018 and 2017, respectively, and net foreign exchange gains of $0.1 million for the year ended December 31, 2016.

The financial statements of the Company's foreign subsidiaries are translated from the functional (local) currency to U.S. Dollars. Assets and liabilities are translated at the exchange rates on the balance sheet date. Results of operations are translated at average exchange rates, which approximate rates in effect when the underlying transactions occurred.

Accumulated Other Comprehensive Loss

Accumulated other comprehensive loss is composed entirely of foreign currency translation adjustments.

Earnings Per Share

Basic earnings per share (EPS) amounts are computed by dividing earnings by the weighted average number of common shares outstanding during the period. Diluted EPS amounts assume the issuance of common stock for all potentially dilutive equivalents outstanding. To the extent stock awards are anti-dilutive, they are excluded from the calculation of diluted EPS.

The details of basic and diluted EPS are as follows:



	Year Ended December 31,
(in thousands, except per share data)	2018		2017		2016
Net income	$	419,375	$	259,251	$	265,636
Weighted average shares outstanding – basic	83,973		84,988		87,227
Dilutive effect of stock plans	1,940		1,866		1,742
Weighted average shares outstanding – diluted	85,913		86,854		88,969
Basic earnings per share	$	4.99	$	3.05	$	3.05
Diluted earnings per share	$	4.88	$	2.98	$	2.99
Anti-dilutive shares	7		84		260

Stock-Based Compensation

The Company accounts for stock-based compensation in accordance with share-based payment accounting guidance. The guidance requires an entity to measure the cost of employee services received in exchange for an award of equity instruments based on the grant-date fair value of the award. The cost is recognized over the period during which an employee is required to provide service in exchange for the award, typically the vesting period.

Fair Value of Financial Instruments

The Company accounts for certain assets and liabilities at fair value in accordance with the accounting guidance applicable to fair value measurements and disclosures. The carrying values of cash, cash equivalents, short-term investments, accounts receivable, accounts payable, accrued expenses, other accrued liabilities and short-term obligations are deemed to be reasonable estimates of their fair values because of their short-term nature.

Revenue from Contracts with Customers

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Revenue from Contract with Customer

Revenue from Contracts with Customers

Adoption of ASC 606, Revenue from Contracts with Customers

The Company adopted ASC 606 on January 1, 2018 using the modified retrospective approach for all contracts not completed as of the date of adoption. Results for reporting periods beginning after January 1, 2018 are presented under ASC 606, while prior period amounts are not adjusted and continue to be reported in accordance with ASC 605, Revenue Recognition (ASC 605). The adoption of ASC 606 represents a change in accounting principle that will more closely align revenue recognition with the delivery of the Company’s software licenses, maintenance and services.

The Company recorded an increase to retained earnings of $242.4 million, or $183.1 million net of tax, on January 1, 2018 due to the cumulative effect of the ASC 606 adoption, with the impact primarily derived from revenue related to time-based software lease licenses.

Impact of ASC 606 on Consolidated Financial Statement Line Items

The following table compares the impacted assets and liabilities on the consolidated balance sheet as of December 31, 2018 to the amounts had ASC 605 been in effect:



	December 31, 2018
(in thousands)	As Reported (ASC 606)		ASC 605		Change
Accounts receivable, less allowance for doubtful accounts of $8,000	$	317,700	$	135,190	$	182,510
Other receivables and current assets	216,113		351,246		(135,133		)
Other long-term assets	82,775		43,429		39,346
Deferred income tax assets	26,630		65,973		(39,343		)
Accrued income taxes	8,726		—		8,726
Other accrued expenses and liabilities	99,559		101,949		(2,390		)
Deferred revenue - current	328,584		526,168		(197,584		)
Deferred income tax liabilities	30,077		23,056		7,021
Other long-term liabilities	61,573		76,354		(14,781		)
Stockholders' equity	$	2,649,547	$	2,403,159	$	246,388

The Company recorded $244.1 million of deferred revenue to retained earnings upon the adoption of ASC 606 on January 1, 2018. The pattern of software lease license revenue recognition has changed under ASC 606. Software lease license revenue was recognized ratably over the term of the contract under the previous guidance; however, approximately 50% of the contract is recognized up front at the commencement of the lease under ASC 606. This change in the pattern of revenue recognition, coupled with the recording of deferred revenue to retained earnings at the adoption date, resulted in the changes to the consolidated balance sheet line items as noted in the table above.

The following table compares the impacted amounts on the consolidated statements of income for the year ended December 31, 2018 to the amounts had ASC 605 been in effect:



(in thousands, except per share data)	As Reported (ASC 606)		ASC 605		Change
Revenue:
Software licenses	$	576,717	$	676,846	$	(100,129	)
Maintenance and service	716,919		539,623		177,296
Cost of sales:
Software licenses	18,619		36,852		(18,233		)
Maintenance and service	110,232		91,999		18,233
Income tax provision	67,710		53,067		14,643
Earnings per share:
Basic	$	4.99	$	4.25	$	0.74
Diluted	$	4.88	$	4.15	$	0.73

The impacts to reported software licenses revenue, and maintenance and service revenue, were primarily due to the PCS portion of lease license contracts now being allocated to maintenance and service revenue under ASC 606. Under the previous guidance, this revenue was reported as software licenses revenue. This decrease to software licenses revenue was partially offset by the upfront recognition of the license component of lease revenue, which would have been recognized ratably over the contract under prior guidance. Consistent with the change in revenue, there was a corresponding reclassification within cost of sales. Costs incurred related to the PCS portion of lease license contracts are reflected in cost of maintenance and service. Under the previous guidance, such costs were reflected within cost of software licenses.

The adoption of ASC 606 had no impact on the Company’s cash flows from operations. However, with the adoption of ASC 606, there will be income tax payments associated with deferred revenue and backlog credited to retained earnings and never recognized as revenue in the financial statements. The 2018 tax payments related to the adoption of ASC 606 are approximately $14.0 million.

Disaggregation of Revenue

The following table summarizes revenue for the years ended December 31, 2018, 2017 and 2016:



	Year Ended December 31,
(in thousands)	2018 (ASC 606)		2018 (ASC 605)		2017 (ASC 605)		2016 (ASC 605)
Revenue:
Lease licenses	$	275,619	$	421,268	$	376,886	$	340,331
Perpetual licenses	301,098		255,578		248,078		227,843
Software licenses	576,717		676,846		624,964		568,174
Maintenance	676,883		499,510		440,428		394,745
Service	40,036		40,113		29,858		25,546
Maintenance and service	716,919		539,623		470,286		420,291
Total revenue	$	1,293,636	$	1,216,469	$	1,095,250	$	988,465

The Company’s software licenses revenue is recognized up front, while maintenance and service revenue is generally recognized over the term of the contract. Under ASC 606, the Company derived 22.4% of its total revenue through the indirect sales channel for the year ended December 31, 2018. Under ASC 605, the Company derived 23.5%, 24.8%, and 24.4% of its total revenue through the indirect sales channel for the years ended December 31, 2018, 2017 and 2016, respectively.

Deferred Revenue

Deferred revenue consists of billings made or payments received in advance of revenue recognition from software license and maintenance agreements. The timing of revenue recognition may differ from the timing of billings to customers. Payment terms vary by the type and location of customer and the products or services offered. The time between invoicing and when payment is due is not significant. The changes in deferred revenue during the year ended December 31, 2018, inclusive of both current and long-term, are as follows:



(in thousands)
Beginning balance – January 1	$	299,730
Acquired deferred revenue	2,470
Recognition of deferred revenue	(1,293,636		)
Deferral of revenue	1,339,964
Currency translation	(5,354		)
Ending balance – December 31	$	343,174

Revenue allocated to remaining performance obligations represents contracted revenue that has not yet been recognized, which includes deferred revenue and backlog. The Company's backlog represents installment billings for periods beyond the current quarterly billing cycle and customer orders received but not processed. Revenue recognized during the year ended December 31, 2018 reflected above of $1,293.6 million included amounts in deferred revenue and backlog at the beginning of the period of $387.2 million. Total revenue allocated to remaining performance obligations was $659.2 million as of December 31, 2018 and will be recognized as revenue as follows:



(in thousands)
Next 12 months	$	475,883
Months 13-24	125,048
Months 25-36	43,470
Thereafter	14,771
Total revenue allocated to remaining performance obligations	$	659,172

Acquisitions

12 Months Ended

Dec. 31, 2018

Business Combinations [Abstract]

Acquisitions

OPTIS

On May 2, 2018, the Company completed the acquisition of 100% of the shares of OPTIS, a premier provider of software for scientific simulation of light, human vision and physics-based visualization, for a purchase price of $291.0 million, paid in cash. The acquisition extends the Company's portfolio into the area of optical simulation to provide comprehensive sensor solutions, covering visible and infrared light, electromagnetics and acoustics for camera, radar and lidar. The acquisition met the definition of a business under ASU 2017-01.

The operating results of OPTIS have been included in the Company's consolidated financial statements since May 2, 2018, the date of acquisition.

The assets and liabilities of OPTIS have been recorded based upon management's estimates of their fair market values as of the acquisition date. The following tables summarize the fair value of consideration transferred and the fair values of identified assets acquired and liabilities assumed at the acquisition date:

Fair Value of Consideration Transferred:



(in thousands)
Cash	$	290,983

Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed:



(in thousands)
Cash	$	7,957
Accounts receivable and other tangible assets	15,979
Developed software and core technologies (9 – 10 year life)	47,597
Customer lists (12 year life)	41,303
Trade names (4 – 10 year life)	10,749
Accounts payable and other liabilities	(11,444		)
Deferred revenue	(2,470		)
Net deferred tax liabilities	(23,187		)
Total identifiable net assets	$	86,484
Goodwill	$	204,499

The goodwill, which is not tax-deductible, is attributed to intangible assets that do not qualify for separate recognition, including the assembled workforce of the acquired business and the synergies expected to arise as a result of the acquisition of OPTIS.

The fair values of the assets acquired and liabilities assumed are based on preliminary calculations. The estimates and assumptions for these items are subject to change as additional information about what was known and knowable at the acquisition date is obtained during the measurement period (up to one year from the acquisition date). During the period since the OPTIS acquisition date, the Company adjusted the fair values of the assets acquired and liabilities assumed, with the offset recorded as a $1.8 million increase to goodwill. These adjustments were based on refinements to assumptions used in the preliminary valuation of accounts receivable and other tangible assets, developed software and core technologies, accounts payable and other liabilities, and information about what was known and knowable as of the acquisition date in the calculation of the net deferred tax liabilities.

In valuing deferred revenue on the OPTIS balance sheet as of the acquisition date, the Company applied the fair value provisions applicable to the accounting for business combinations. Acquired deferred revenue with a historical carrying value of $14.2 million under ASC 606, and $22.3 million under ASC 605, was ascribed a fair value of $2.5 million on the opening balance sheet. As a result, the Company's post-acquisition revenue will be less than the sum of what would have otherwise been reported by ANSYS and OPTIS absent the acquisition. Under ASC 606 and ASC 605, the impacts on reported revenue for the year ended December 31, 2018 were $8.7 million and $14.4 million, respectively. The expected impact on reported revenue for the year ending December 31, 2019 is $1.6 million under ASC 606.

Full pro forma results of operations have not been presented as the effects of the OPTIS business combination were not material to the Company's consolidated results of operations. The table presented below reflects the impact of OPTIS from the date of acquisition to December 31, 2018. The operating loss does not include integration costs borne directly by ANSYS, Inc. and its non-OPTIS subsidiaries as a result of the acquisition.



	Year Ended December 31, 2018
(in thousands)	ASC 606			ASC 605
Revenue	$	18,532		$	12,276
Operating loss	$	(5,462	)	$	(11,718	)

Prior Year Acquisitions

During the years ended December 31, 2017 and 2016, the Company completed various acquisitions to expand its customer base and accelerate the development of new and innovative products to the marketplace while lowering design and engineering costs for customers. The acquisitions were not individually significant. The combined purchase prices of the acquisitions purchased during the years ended December 31, 2017 and 2016 were approximately $67.0 million and $10.3 million, respectively. The 2017 technology acquisitions are further described in the table below:



Date of Closing	Company	Details
November 15, 2017	3DSIM	3DSIM, a developer of premier additive manufacturing technology, gives ANSYS a complete additive manufacturing simulation workflow solution. 3DSIM's software solutions empower manufacturers, designers, materials scientists and engineers to achieve their objectives through simulation-driven innovation rather than physical trial and error.
July 5, 2017	Computational Engineering International, Inc. (CEI Inc.)	CEI Inc., the developer of EnSight, aids engineers and scientists in their ability to analyze, visualize and communicate large simulation data sets in clear, higher-resolution outputs.
March 10, 2017	CLK Design Automation (CLK-DA)	CLK-DA offers fast transistor simulation technology that complements the Company's semiconductor product portfolio.

The operating results of each acquisition have been included in the Company's consolidated financial statements since each respective date of acquisition. The effects of the business combinations were not material to the Company's consolidated results of operations individually or in the aggregate.

In valuing deferred revenue on the balance sheets of the Company's acquisitions as of their respective acquisition dates, the Company applied the fair value provisions applicable to the accounting for business combinations. Under ASC 606, the impacts on reported revenue for the year ended December 31, 2018 were $0.7 million. The expected impact on reported revenue for the year ending December 31, 2019 is $0.1 million. Under ASC 605, the impacts on reported revenue for the years ended December 31, 2018, 2017 and 2016 were $1.2 million, $2.9 million and $0.1 million, respectively.

Receivables and Other Current Assets

12 Months Ended

Dec. 31, 2018

Prepaid Expense and Other Assets, Current [Abstract]

Receivables and Other Current Assets

The Company's receivables and other current assets comprise the following balances:



	December 31,
(in thousands)	2018		2017
Accounts receivable, less allowance for doubtful accounts of $8,000 and $6,800, respectively	$	317,700	$	124,659

Receivables related to unrecognized revenue	$	167,144	$	215,155
Income taxes receivable, including overpayments and refunds	13,709		21,663
Prepaid expenses and other current assets	35,260		27,002
Total other receivables and current assets	$	216,113	$	263,820

Receivables for unrecognized revenue represent the current portion of billings made for customer contracts that have not yet been recognized as revenue.

Upon the adoption of ASC 606 on January 1, 2018, the opening balances of accounts receivable and receivables related to unrecognized revenue were $278.8 million and $136.4 million, respectively.

Property and Equipment

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property and Equipment

Property and equipment consists of the following:



		December 31,
(in thousands)	Estimated Useful Lives	2018			2017
Equipment	1-12 years	$	92,409		$	88,189
Computer software	1-5 years	35,053			34,994
Buildings and improvements	5-40 years	27,352			26,423
Leasehold improvements	1-17 years	15,782			13,316
Furniture	1-13 years	10,846			9,239
Land		1,759			1,759
Property and equipment, gross		183,201			173,920
Less: Accumulated depreciation		(121,546		)	(116,824		)
Property and equipment, net		$	61,655		$	57,096

Depreciation expense related to property and equipment was $18.4 million, $17.9 million and $18.7 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Goodwill and Intangible Assets

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

Goodwill represents the excess of the fair value of the consideration transferred over the value of net tangible and identifiable intangible assets of acquired businesses. Identifiable intangible assets acquired in business combinations are recorded based on their fair values on the date of acquisition.

During the first quarter of 2018, the Company completed the annual impairment test for goodwill and the indefinite-lived intangible asset and determined that these assets had not been impaired as of the test date, January 1, 2018. No other events or circumstances changed during the year ended December 31, 2018 that would indicate that the fair values of the Company's reporting unit and indefinite-lived intangible asset are below their carrying values.

The Company's intangible assets and estimated useful lives are classified as follows:



	December 31, 2018					December 31, 2017
(in thousands)	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
Finite-lived intangible assets:
Developed software and core technologies (3 – 11 years)	$	410,680	$	(314,730	)	$	365,317	$	(297,645	)
Customer lists and contract backlog (5 – 15 years)	209,031		(117,614		)	171,048		(104,522		)
Trade names (2 – 10 years)	137,225		(113,677		)	127,200		(104,130		)
Total	$	756,936	$	(546,021	)	$	663,565	$	(506,297	)
Indefinite-lived intangible assets:
Trade name	$	357				$	357

Amortization expense for the intangible assets reflected above was $40.8 million, $49.8 million and $50.8 million for the years ended December 31, 2018, 2017 and 2016, respectively.

As of December 31, 2018, estimated future amortization expense for the intangible assets reflected above is as follows:



(in thousands)
2019	$	31,652
2020	32,723
2021	29,900
2022	26,182
2023	23,275
Thereafter	67,183
Total intangible assets subject to amortization, net	210,915
Indefinite-lived trade name	357
Other intangible assets, net	$	211,272

The changes in goodwill during the years ended December 31, 2018 and 2017 are as follows:



(in thousands)	2018			2017
Beginning balance - January 1	$	1,378,553		$	1,337,215
Acquisitions and adjustments⁽¹⁾	204,381			36,443
Currency translation	(10,479		)	4,895
Ending balance - December 31	$	1,572,455		$	1,378,553

⁽¹⁾ In accordance with the accounting for business combinations, the Company recorded adjustments to goodwill for the effect of changes in the provisional fair values of the assets acquired and liabilities assumed during the measurement period (up to one year from the acquisition date) as the Company obtained new information about facts and circumstances that existed as of the acquisition date that, if known, would have affected the measurement of the amounts recognized as of that date.

Fair Value Measurement

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurement

The valuation hierarchy for disclosure of assets and liabilities reported at fair value prioritizes the inputs for such valuations into three broad levels:


•	Level 1: quoted prices (unadjusted) in active markets for identical assets or liabilities;


•	Level 2: quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument; or


•	Level 3: unobservable inputs based on the Company's own assumptions used to measure assets and liabilities at fair value.

A financial asset's or liability's classification within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement.

The following tables provide the assets carried at fair value and measured on a recurring basis:



			Fair Value Measurements at Reporting Date Using:
(in thousands)	December 31, 2018		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents	$	446,055	$	446,055	$	—	$	—
Short-term investments	$	225	$	—	$	225	$	—
Deferred compensation plan investments	$	1,646	$	1,646	$	—	$	—



			Fair Value Measurements at Reporting Date Using:
(in thousands)	December 31, 2017		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents	$	312,914	$	312,914	$	—	$	—
Short-term investments	$	286	$	—	$	286	$	—
Deferred compensation plan investments	$	3,742	$	3,742	$	—	$	—

The cash equivalents in the preceding tables represent money market funds, valued at net asset value, with carrying values which approximate their fair values because of their short-term nature.

The short-term investments in the preceding tables represent deposits held by certain foreign subsidiaries of the Company. The deposits have fixed interest rates with original maturities ranging from three months to one year.

The deferred compensation plan investments in the preceding tables represent trading securities held in a rabbi trust for the benefit of the non-employee Directors. These securities consist of mutual funds traded in an active market with quoted prices. As a result, the plan assets are classified as Level 1 in the fair value hierarchy. The plan assets are recorded within other long-term assets on the Company's consolidated balance sheets.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

Income before income taxes includes the following components:



	Year Ended December 31,
(in thousands)	2018		2017		2016
Domestic	$	455,478	$	344,447	$	340,251
Foreign	31,607		51,247		40,064
Total	$	487,085	$	395,694	$	380,315

The provision for income taxes is composed of the following:



	Year Ended December 31,
(in thousands)	2018			2017			2016
Current:
Federal	$	58,138		$	112,414		$	99,783
State	12,888			7,879			8,338
Foreign	30,359			18,843			17,479
Deferred:
Federal	(20,764		)	(7,387		)	(13,368		)
State	(2,901		)	(584		)	(1,036		)
Foreign	(10,010		)	5,278			3,483
Total	$	67,710		$	136,443		$	114,679

The reconciliation of the U.S. federal statutory tax rate to the consolidated effective tax rate is as follows:



	Year Ended December 31,
	2018		2017		2016
Federal statutory tax rate	21.0	%	35.0	%	35.0	%
State income taxes, net of federal benefit	1.5		1.1		1.6
Foreign rate differential	0.8		0.1		0.1
Uncertain tax positions	0.5		0.3		(0.2	)
U.S. tax reform enactment	0.2		4.5		—
Domestic production activity benefit	—		(2.6	)	(3.7	)
Benefit from entity structuring activities	(1.4	)	—		(2.2	)
Research and development credits	(2.3	)	(1.4	)	(1.0	)
Stock-based compensation	(3.3	)	(3.1	)	0.2
Foreign-derived intangible income deduction	(3.9	)	—		—
Other	0.8		0.6		0.4
	13.9	%	34.5	%	30.2	%

On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (Tax Reform). Tax Reform makes broad and complex changes to the U.S. tax code, including, but not limited to, (1) reducing the U.S. federal corporate tax rate from 35 percent to 21 percent; (2) requiring companies to pay a one-time federal income tax on certain unrepatriated earnings of foreign subsidiaries (transition tax); (3) generally eliminating U.S. federal income taxes on dividends from foreign subsidiaries; (4) creating a new provision designed to tax global intangible low-taxed income (GILTI) which allows for the possibility of using foreign tax credits (FTCs) and a deduction of up to 50 percent to offset the income tax liability (subject to some limitations); (5) repealing the domestic production activity deduction; (6) creating the foreign-derived intangible income deduction; (7) creating the base erosion anti-abuse tax, a new minimum tax; (8) allowing for full expensing of qualified property through bonus depreciation; and (9) creating limitations on the deductibility of certain executive compensation.

The SEC staff issued Staff Accounting Bulletin (SAB) 118, which provides guidance on accounting for the tax effects of Tax Reform. SAB 118 provided a measurement period that was limited to one year from enactment for companies to complete the accounting under ASC 740, Income Taxes. In accordance with SAB 118, throughout the measurement period, a company must reflect the income tax effects of those aspects of Tax Reform for which the accounting under ASC 740 was complete in the financial statements. To the extent that a company’s accounting for certain income tax effects of Tax Reform was incomplete, but a reasonable estimate was able to be made, the company must record a provisional estimate in the financial statements. If a company could not determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the tax laws that were in effect immediately before the enactment of Tax Reform.

As further discussed below, the Company finalized its provisional Tax Reform calculations as of the end of the measurement period, based on guidance and information available as of the reporting date. The U.S. government has not yet issued final guidance related to the new rules enacted as part of Tax Reform. Subsequent adjustments, if any, will be recorded in the period in which guidance is finalized.

The Company’s accounting for the impact of the reduction in the U.S. federal corporate tax rate on the Company's deferred tax assets and liabilities is complete. Tax Reform reduced the corporate tax rate to 21 percent, effective January 1, 2018. Consequently, the Company recorded a net adjustment to deferred income tax expense of $1.9 million for the year ended December 31, 2017 to revalue the Company’s deferred tax assets and liabilities. No further adjustments were recorded for the year ended December 31, 2018.

The Company’s accounting for the transition tax is complete. Reasonable estimates of certain effects were calculated and a provisional adjustment of $16.0 million was recorded in the December 31, 2017 financial statements. To determine the amount of the transition tax, the Company determined, in addition to other factors, the amount of post-1986 earnings and profits (E&P) of the relevant subsidiaries, as well as the amount of non-U.S. income taxes paid on such earnings. Based on revised E&P calculations updated during the measurement period, the Company recognized an additional measurement-period adjustment of $0.9 million to the transition tax obligation and a corresponding adjustment to tax expense, resulting in a total transition tax obligation of $16.9 million. The Company has elected to pay this liability over eight years; however, in accordance with IRS issued guidance, tax overpayments from the year ended December 31, 2017 are required to be applied to the transition tax obligation. Based on this guidance, $15.6 million of the obligation has been paid, with the remaining $1.3 million recorded in other long-term liabilities at December 31, 2018.

The Company’s accounting for the indefinite reinvestment assertion is complete. In general, it is the practice and intention of the Company to repatriate previously taxed earnings in excess of working capital needs and to reinvest all other earnings of its non-U.S. subsidiaries. As part of Tax Reform, the Company incurred U.S. tax on substantially all of the earnings of its non-U.S. subsidiaries as part of the transition tax. This tax increased the Company’s previously taxed earnings and allows for the repatriation of the majority of its foreign earnings without any residual U.S. federal tax. The Company does not believe that there is an excess of the financial reporting basis over the tax basis of investments in foreign subsidiaries. Accordingly, any repatriation in excess of previously taxed earnings will be a non-taxable return of basis. During the year ended December 31, 2018, the Company repatriated $144.3 million of foreign cash. The Company has not made any measurement-period adjustments related to its indefinite reinvestment assertion during the year ended December 31, 2018.

The Company’s accounting policy choice for GILTI is complete. Under U.S. GAAP, the Company is allowed to make an accounting policy choice of either (1) treating taxes due on future U.S. inclusions in taxable income related to GILTI as a current-period expense when incurred (the period cost method) or (2) factoring such amounts into the Company’s measurement of its deferred taxes (the deferred method). The Company selected the period cost method and recorded GILTI tax expense of $0.4 million in the financial statements for the year ended December 31, 2018.

The components of deferred tax assets and liabilities are as follows:



	December 31,
(in thousands)	2018			2017
Deferred tax assets:
Stock-based compensation	$	20,464		$	17,825
Net operating loss carryforwards	19,741			21,391
Uncertain tax positions	17,823			15,424
Employee benefits	15,048			8,603
Research and development credits	5,951			3,699
Allowance for doubtful accounts	1,616			1,462
Deferred revenue	—			5,134
Other	2,505			2,003
Valuation allowance	(2,127		)	(1,906		)
	81,021			73,635
Deferred tax liabilities:
Other intangible assets	(38,787		)	(29,924		)
Accounting method change	(31,626		)	—
Deferred revenue	(12,021		)	—
Property and equipment	(2,034		)	(1,557		)
Unremitted foreign earnings	—			(1,504		)
	(84,468		)	(32,985		)
Net deferred tax (liabilities) assets	$	(3,447	)	$	40,650

At December 31, 2018 and 2017, respectively, the Company excluded from the above table deferred tax assets associated with foreign net operating loss carryforwards of $19.5 million and $25.2 million and corresponding valuation allowances of $19.5 million and $25.2 million in a jurisdiction where the Company determined utilization is remote.

The net increase in the valuation allowance was primarily due to an increase in unrealizable tax assets. As of each reporting date, management considers new evidence, both positive and negative, that could affect the future realization of deferred tax assets. If management determines it is more likely than not that an asset, or a portion of an asset, will not be realized, a valuation allowance is recorded.

As of December 31, 2018, the Company had federal net operating loss carryforwards of $5.6 million. These losses expire between 2025 - 2036, and are subject to limitations on their utilization. Deferred tax assets of $0.4 million have been recorded for state operating loss carryforwards. These losses expire between 2029 - 2035, and are subject to limitations on their utilization. The Company had total foreign net operating loss carryforwards of $73.8 million, of which $46.0 million are not currently subject to expiration dates. The remainder, $27.8 million, expires between 2021 - 2035. The Company had tax credit carryforwards of $4.3 million, of which $2.2 million are subject to limitations on their utilization. Approximately $0.6 million of these tax credit carryforwards are not currently subject to expiration dates. The remainder, $3.7 million, expires in various years between 2019 - 2038.

The following is a reconciliation of the total amounts of unrecognized tax benefits:



	Year Ended December 31,
(in thousands)	2018			2017			2016
Unrecognized tax benefit as of January 1	$	19,657		$	15,209		$	16,067
Gross increases—tax positions in prior period	1,229			905			983
Gross decreases—tax positions in prior period	(376		)	(765		)	(2,502		)
Gross increases—tax positions in current period	4,014			3,757			2,725
Reductions due to a lapse of the applicable statute of limitations	(994		)	(847		)	(927		)
Changes due to currency fluctuation	(703		)	1,414			(348		)
Settlements	—			(16		)	(789		)
Unrecognized tax benefit as of December 31	$	22,827		$	19,657		$	15,209

The Company believes that it is reasonably possible that approximately $1.0 million of uncertain tax positions may be resolved within the next twelve months as a result of settlement with a taxing authority or a lapse of the statute of limitations. Of the total unrecognized tax benefit as of December 31, 2018, $13.7 million would affect the effective tax rate, if recognized.

The Company recognizes interest and penalties related to income taxes as income tax expense. During the years ended December 31, 2018, 2017 and 2016, the Company recorded penalty expense of $0.8 million, $1.1 million and $0.8 million, respectively. The Company recorded interest income of $0.1 million for the year ended December 31, 2018 and interest expense of $0.4 million and $0.1 million during the years ended December 31, 2017 and 2016, respectively. As of December 31, 2018, the Company accrued a liability for penalties of $4.7 million and interest of $4.0 million. As of December 31, 2017, the Company accrued a liability for penalties of $3.9 million and interest of $3.6 million.

The Company is subject to taxation in the U.S. and various states and foreign jurisdictions. In the U.S., the Company's only major tax jurisdiction, the 2015 - 2018 tax years are open to examination by the Internal Revenue Service.

Pension And Profit-Sharing Plans	12 Months Ended
Pension And Profit-Sharing Plans	Dec. 31, 2018
Retirement Benefits [Abstract]
Pension And Profit-Sharing Plans	Pension and Profit-Sharing Plans The Company has a 401(k)/profit-sharing plan for all qualifying domestic employees that permits participants to defer a portion of their pay pursuant to Section 401(k) of the Internal Revenue Code. The Company makes matching contributions on behalf of each eligible participant in an amount equal to 100% of the first 3% and an additional 25% of the next 5%, for a maximum total of 4.25% of the employee's compensation. The Company may make a discretionary contribution based on the participant's eligible compensation, provided the employee is employed at the end of the year and has worked at least 1,000 hours. The Company also maintains various defined contribution and defined benefit pension arrangements for its international employees. The Company meets the minimum statutory funding requirements for its foreign defined benefit and contribution plans. The total unfunded portion of the defined benefit obligations is $9.7 million. Expenses related to the Company's retirement programs were $12.4 million in 2018, $10.1 million in 2017 and $9.1 million in 2016.

Non-Compete and Employment Agreements	12 Months Ended
Non-Compete and Employment Agreements	Dec. 31, 2018
Non-Compete and Employment Agreements [Abstract]
Non-Compete and Employment Agreements	Non-Compete and Employment Agreements Employees of the Company have signed agreements under which they have agreed not to disclose trade secrets or confidential information that, where legally permitted, restrict engagement in or connection with any business that is competitive with the Company anywhere in the world while employed by the Company (and, in some cases, for specified periods thereafter in relevant geographic areas), and that any products or technology created by them during their term of employment are the property of the Company. In addition, the Company requires all channel partners to enter into agreements not to disclose the Company's trade secrets and other proprietary information. The Company has an employment agreement with its Chief Executive Officer. This agreement provides for, among other things, in the case of termination for reasons other than death, disability or cause and subject to non-compete and non-solicit clauses, minimum severance payments equal to two times his base salary and target bonus paid out over two years from the date of termination and up to two years of payments for health care coverage from the date of termination. The Chief Executive Officer is subject to a two-year restriction on competition and solicitation following termination of employment under the circumstances described in the contract. The Company has a transition agreement with its Chairman of the Board. This agreement provides for, among other things, that the Chairman of the Board shall be employed by the Company until April 30, 2019 unless terminated earlier in accordance with the terms of the agreement. The Chairman of the Board shall receive salary paid in bi-monthly installments as specified in the transition agreement and restricted stock units vesting in part in March 2018 and the remainder at the end of the transition agreement, subject to the Chairman of the Board's continued employment, in accordance with the terms of the transition agreement. The Chairman of the Board will not be entitled to bonus payments during his employment pursuant to the transition agreement, but he will be eligible to participate in all of the Company’s benefit plans subject to the terms of such plans. The transition agreement provides for an additional payment (less salary received and equity calculations as set forth in the transition agreement) in the event that the Chairman of the Board's employment is terminated without cause prior to April 30, 2019. The Company also has employment agreements with several other employees, primarily in foreign jurisdictions. The terms of these employment agreements generally include annual compensation, severance payment provisions and non-compete clauses.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

The Company has an equity incentive plan—the Fifth Amended and Restated ANSYS, Inc. 1996 Stock Option and Grant Plan (Stock Plan). The Stock Plan, as amended, authorizes the grant of up to 39.8 million shares of the Company's common stock in the form of: (i) incentive stock options (ISOs), (ii) nonqualified stock options, (iii) common stock with or without vesting or other restrictions, (iv) common stock upon the attainment of specified performance goals, (v) restricted stock awards, (vi) the right to receive cash dividends with the holders of the common stock as if the recipient held a specified number of shares of the common stock, (vii) deferred stock awards, (viii) restricted stock unit awards, (ix) stock appreciation rights and (x) cash-based awards.

The Stock Plan provides that: (i) the exercise price of an ISO must be no less than the fair value of the stock at the date of grant and (ii) the exercise price of an ISO held by an optionee who possesses more than 10% of the total combined voting power of all classes of stock must be no less than 110% of the fair market value of the stock at the time of grant. The Compensation Committee of the Board of Directors has the authority to set expiration dates no later than ten years from the date of grant (or five years for an optionee who meets the 10% criterion), payment terms, and other provisions for each grant. The majority of options granted have a four-year vesting period. Shares associated with unexercised options or reacquired shares of common stock (except those shares withheld as a result of tax withholding or net issuance) become available for option grants and common stock issuances under the Stock Plan. The Compensation Committee of the Board of Directors may, at its sole discretion, accelerate or extend the date or dates on which all or any particular award or awards granted under the Stock Plan may vest or be exercised. Upon termination of service of a participant due to the participant’s death or disability, the vesting of restricted stock units held by the participant accelerates (in case of performance-based vesting, subject to the attainment of the performance requirement).

In the event of a "sale event," defined in the Stock Plan as a "Transaction," all outstanding awards will be assumed or continued by the successor entity, with appropriate adjustment in the awards to reflect the transaction. In such event, except as the Compensation Committee may otherwise specify with respect to particular awards in the award agreements, if the service relationship of the holder of an award is terminated without cause within 18 months after the sale event, then all awards held by such holder will become fully vested and exercisable at that time. If there is a sale event in which the successor entity refuses to assume or continue outstanding awards, then subject to the consummation of the sale event, all awards with time-based vesting conditions will become fully vested and exercisable at the effective time of the sale event and all awards with performance-based vesting conditions may become vested and exercisable in accordance with the award agreements at the discretion of the Compensation Committee. If awards are not assumed or continued after a sale event, then all such awards will terminate at the time of the sale event. In the event of the termination of stock options or stock appreciation rights in connection with a sale event, the Compensation Committee may either make or provide for a cash payment to the holders of such awards equal to the difference between the per share transaction consideration and the exercise price of such awards or permit each holder to have at least a 15-day period to exercise such awards prior to their termination.

The Company currently issues shares related to exercised stock options or vested awards from its existing pool of treasury shares and has no specific policy to repurchase treasury shares as stock options are exercised or as awards vest. If the treasury pool is depleted, the Company will issue new shares.

Total stock-based compensation expense recognized for the years ended December 31, 2018, 2017 and 2016 is as follows:



	Year Ended December 31,
(in thousands, except per share amounts)	2018			2017			2016
Cost of sales:
Software licenses	$	—		$	969		$	701
Maintenance and service	5,224			2,533			1,578
Operating expenses:
Selling, general and administrative	47,099			30,817			15,990
Research and development	31,023			18,835			15,078
Stock-based compensation expense before taxes	83,346			53,154			33,347
Related income tax benefits	(34,518		)	(20,503		)	(10,538		)
Stock-based compensation expense, net of taxes	$	48,828		$	32,651		$	22,809
Net impact on earnings per share:
Basic earnings per share	$	(0.58	)	$	(0.38	)	$	(0.26	)
Diluted earnings per share	$	(0.57	)	$	(0.38	)	$	(0.26	)

Stock Options

Information regarding stock option transactions is summarized below:



	Year Ended December 31,
	2018				2017				2016
(options in thousands)	Options		Weighted- Average Exercise Price		Options		Weighted- Average Exercise Price		Options		Weighted- Average Exercise Price
Outstanding, beginning of year	2,170		$	59.17	3,136		$	56.37	3,986		$	51.07
Granted	—		$	—	—		$	—	260		$	94.38
Exercised	(679	)	$	50.92	(956	)	$	49.78	(1,082	)	$	45.57
Forfeited	(7	)	$	86.28	(10	)	$	80.92	(28	)	$	72.07
Outstanding, end of year	1,484		$	62.80	2,170		$	59.17	3,136		$	56.37
Vested and Exercisable, end of year	1,347		$	59.69	1,930		$	55.11	2,762		$	51.80
Nonvested	137		$	93.44	240		$	91.71	374		$	90.12



	2018		2017		2016
Weighted Average Remaining Contractual Term (in years)
Outstanding	3.55		4.10		4.62
Vested and Exercisable	3.14		3.57		4.04
Nonvested	7.60		8.30		8.93
Aggregate Intrinsic Value (in thousands)
Exercised	$	78,648	$	58,472	$	49,752
Outstanding	$	118,908	$	191,895	$	113,822
Vested and Exercisable	$	112,133	$	178,456	$	112,379
Nonvested	$	6,775	$	13,439	$	1,443
Compensation Expense - Stock Options (in thousands)	$	2,006	$	2,948	$	7,406

Historical and future expected forfeitures have not been significant and, as a result, the outstanding option amounts reflected in the tables above approximate the options expected to vest.

The fair value of each option grant is estimated on the date of grant, or date of acquisition for options issued in a business combination, using the Black-Scholes option pricing model, which was developed for use in estimating the fair value of traded options that have no vesting restrictions and are fully transferable. The Company's options have characteristics significantly different from those of traded options, and changes in input assumptions can materially affect the fair value estimates. The interest rates used were determined by using the five-year Treasury Note yield at the date of grant or date of acquisition for options issued in a business combination. The volatility was determined based on the historic volatility of the Company's stock during the preceding six years.

The table below presents the weighted average input assumptions used and resulting fair values for options granted or issued in business combinations during the year ended December 31, 2016:



Risk-free interest rate	1.19% to 1.93%
Expected dividend yield	—%
Expected volatility	24%
Expected term	5.7 years
Weighted average fair value per share	$23.96

The Company did not grant stock option awards in 2018 and 2017. Forfeitures of awards are accounted for as they occur. The effect of pre-vesting forfeitures on the Company's recorded expense has historically been negligible due to the relatively low turnover of stock option holders.

The Company's determination of fair value of share-based payment awards on the date of grant using an option pricing model is affected by the Company's stock price as well as assumptions regarding a number of variables. As of December 31, 2018, total unrecognized estimated compensation cost related to unvested stock options granted prior to that date was $2.8 million, which is expected to be recognized over a weighted average period of 1.4 years.

Information regarding stock options outstanding as of December 31, 2018 is summarized below:



(options in thousands)	Options Outstanding				Options Exercisable				Options Unvested
Range of Exercise Prices	Options	Weighted- Average Remaining Contractual Life (years)	Weighted- Average Exercise Price		Options	Weighted- Average Remaining Contractual Life (years)	Weighted- Average Exercise Price		Options	Weighted- Average Remaining Contractual Life (years)	Weighted- Average Exercise Price
$5.91 - $48.97	458	1.57	$	42.12	457	1.56	$	42.20	1	6.00	$	12.26
$58.67	359	2.84	$	58.67	359	2.84	$	58.67	—	0.00	$	—
$61.68 - $65.72	11	0.44	$	63.75	11	0.44	$	63.75	—	0.00	$	—
$67.44 - $95.09	656	5.38	$	79.50	520	4.79	$	75.68	136	7.61	$	94.16

Restricted Stock Units

Under the terms of the ANSYS, Inc. Second Amended and Restated Long-Term Incentive Plan, the Company issues various restricted stock awards. The following table summarizes the types of awards and vesting conditions:



Award	Vesting Period	Vesting Condition
Restricted stock units with a market and service condition	Three years	Company performance measured by total shareholder return relative to the Nasdaq Composite Index for the measurement period and subject to continued employment through the vesting period.
Restricted stock units with an operating performance and service condition	Three years	Operating performance metrics as defined by the Company through the vesting period.
Restricted stock units with a service condition only	Three or four years	Continued employment with the Company through the yearly vesting period.

The fair values of restricted stock units (RSUs) with a market condition were estimated using a Monte Carlo simulation model and are recognized over the vesting period. The determination of the fair values of the awards was affected by the grant date and several variables, each of which has been identified in the chart below:



	Year Ended December 31,
Assumptions used in Monte Carlo lattice pricing model	2018	2017	2016
Risk-free interest rate	2.4%	1.5%	1.0%
Expected dividend yield	—%	—%	—%
Expected volatility—ANSYS stock price	21%	19%	21%
Expected volatility—Nasdaq Composite Index	15%	15%	16%
Expected term	2.8 years	2.8 years	2.8 years
Correlation factor	0.65	0.70	0.65
Weighted average fair value per share	191.76	120.94	78.71

The fair value of RSUs with operating performance metrics is based on the fair market value of the Company's stock on the date of the grant and is recognized from the grant date through the conclusion of the measurement period associated with each operating performance metric based on management's estimates concerning the probability of vesting.

The fair value of RSUs with only a service condition is based on the fair market value of the Company's stock on the date of the grant and is recognized over the vesting period.

Total compensation expense for RSU awards recorded for the years ended December 31, 2018, 2017 and 2016 was $77.4 million, $46.3 million and $22.9 million, respectively.

Information regarding all employee RSU transactions is summarized below:



	Year Ended December 31,
	2018				2017				2016
(RSUs in thousands)	RSUs		Weighted- Average Grant Date Fair Value		RSUs		Weighted- Average Grant Date Fair Value		RSUs		Weighted- Average Grant Date Fair Value
Nonvested, beginning of year	1,361		$	100.66	906		$	86.45	656		$	83.30
Granted⁽¹⁾	681		$	163.67	866		$	109.67	588		$	87.50
Performance adjustment⁽²⁾	76		$	151.52	35		$	98.29	(90	)	$	77.68
Vested	(524	)	$	101.38	(341	)	$	88.58	(176	)	$	83.79
Forfeited	(72	)	$	125.29	(105	)	$	90.80	(72	)	$	83.82
Nonvested, end of year	1,522		$	129.96	1,361		$	100.66	906		$	86.45

⁽¹⁾Includes all RSUs granted during the year. RSUs with operating performance conditions are issued annually and have three performance cycles. Performance conditions are assigned at the beginning of each performance cycle and are reflected as grants at target at that time.

⁽²⁾RSUs with a market or performance condition are granted at target and vest based on achievement of the market or operating performance and service conditions. The actual number of RSUs issued may be more or less than the target RSUs depending on the achievement of the market or operating performance conditions.

Board of Directors

In 2015 and prior, the Company granted deferred stock awards to non-employee Directors, which are rights to receive shares of common stock upon termination of service as a Director. Associated with these awards, the Company established a non-qualified 409(a) deferred compensation plan with assets held under a rabbi trust to provide Directors an opportunity to diversify their vested awards. During open trading windows and at their elective option, the Directors may convert their Company shares into a variety of non-Company-stock investment options in order to diversify a portion of their holdings, subject to meeting ownership guidelines.

Information regarding deferred stock awards to non-employee Directors is summarized below:



	Year Ended December 31, 2018
	Diversified		Undiversified		Total
Deferred Awards Outstanding, beginning of year	29,500		159,599		189,099
Shares Diversified	6,105		(6,105	)	—
Shares Issued Upon Retirement	(23,355	)	(33,045	)	(56,400	)
Deferred Awards Outstanding, end of year	12,250		120,449		132,699

In 2018, 2017 and 2016, the Company granted 13,632, 18,018 and 38,400 RSUs, respectively, which will vest in full upon the earlier of one year from the date of grant or the date of the next regular meeting of stockholders. The weighted average grant date fair values per RSU were $165.71, $123.38 and $86.25 for the years ended December 31, 2018, 2017 and 2016, respectively. Total compensation expense associated with the awards recorded for the years ended December 31, 2018, 2017 and 2016 was $2.3 million, $2.6 million and $1.9 million, respectively.

Employee Stock Purchase Plan

The Company's 1996 Employee Stock Purchase Plan (the “Purchase Plan”) was adopted by the Board of Directors on April 19, 1996 and was subsequently approved by the Company's stockholders. The stockholders approved an amendment to the Purchase Plan in May 2016 to increase the number of shares available for offerings to 1.8 million shares. The Purchase Plan is administered by the Compensation Committee. Offerings under the Purchase Plan commence on each February 1 and August 1, and have a duration of six months. An employee who owns or is deemed to own shares of stock representing in excess of 5% of the combined voting power of all classes of stock of the Company may not participate in the Purchase Plan.

During each offering, an eligible employee may purchase shares under the Purchase Plan by authorizing payroll deductions of up to 10% of his or her cash compensation during the offering period. The maximum number of shares that may be purchased by any participating employee during any offering period is limited to 3,840 shares (as adjusted by the Compensation Committee from time to time). Unless the employee has previously withdrawn from the offering, his or her accumulated payroll deductions will be used to purchase common stock on the last business day of the period at a price equal to 90% of the fair market value of the common stock on the first or last day of the offering period, whichever is lower. Under applicable tax rules, an employee may not accrue the right to purchase more than $25,000 of common stock, based on the grant-date fair value, in any calendar year in which the option is outstanding at any time. As of December 31, 2018, 1.6 million shares of common stock had been issued under the Purchase Plan. The total compensation expense recorded under the Purchase Plan during the years ended December 31, 2018, 2017 and 2016 was $1.8 million, $1.2 million and $1.2 million, respectively.

Stock Repurchase Program

12 Months Ended

Dec. 31, 2018

Class of Stock Disclosures [Abstract]

Stock Repurchase Program

Under the Company's stock repurchase program, the Company repurchased shares as follows:



	Year Ended December 31,
(in thousands, except per share data)	2018		2017		2016
Number of shares repurchased	1,674		2,750		3,700
Average price paid per share	$	161.12	$	122.20	$	90.90
Total cost	$	269,801	$	336,042	$	336,335

The most recent amendment to the program, authorizing the repurchase of up to 5.0 million shares, was approved by the Company's Board of Directors in February 2018. There is no expiration date to this amendment. As of December 31, 2018, 3.8 million shares remained available for repurchase under the program.

Leases

12 Months Ended

Dec. 31, 2018

Leases [Abstract]

Leases

Office Space

The Company's executive offices and those related to certain domestic product development, marketing, production and administration are located in a 186,000 square foot office facility in Canonsburg, Pennsylvania. The term of the lease is 183 months, beginning on October 1, 2014 and expiring on December 31, 2029. Absent the exercise of options in the lease for additional rentable space or early lease termination, the Company's base rent (inclusive of property taxes and certain operating expenses) will be $4.3 million per annum for the first five years of the lease term, $4.5 million per annum for years six through ten and $4.7 million per annum for years eleven through fifteen. The Company incurred $4.4 million in lease expense related to this facility during each of the years ended December 31, 2018, 2017 and 2016.

The Company has entered into various other noncancellable operating leases for office space.

Office space lease expense totaled $19.9 million, $17.1 million and $16.9 million for the years ended December 31, 2018, 2017 and 2016, respectively. Future minimum lease payments, including termination fees, under noncancellable operating leases for office space in effect at December 31, 2018 are as follows:



(in thousands)
2019	$	16,354
2020	12,469
2021	10,177
2022	8,523
2023	6,809
Thereafter	14,267
Total	$	68,599

Royalty Agreements	12 Months Ended
Royalty Agreements	Dec. 31, 2018
Royalty Agreements [Abstract]
Royalty Agreements	Royalty Agreements The Company has entered into various renewable, nonexclusive license agreements under which the Company has been granted access to the licensor's technology and the right to sell the technology in the Company's product line. Royalties are payable to developers of the software at various rates and amounts, which generally are based upon unit sales, revenue or flat fees. Royalty fees are reported in cost of goods sold and were $16.9 million, $16.0 million and $13.1 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Geographic Information

12 Months Ended

Dec. 31, 2018

Segments, Geographical Areas [Abstract]

Geographic Information

Revenue to external customers is attributed to individual countries based upon the location of the customer. Revenue by geographic area is as follows:



	Year Ended December 31,
(in thousands)	2018 (ASC 606)		2018 (ASC 605)		2017 (ASC 605)		2016 (ASC 605)
United States	$	506,335	$	480,997	$	417,343	$	367,892
Japan	145,951		137,733		126,097		120,159
Germany	140,506		124,729		108,211		99,820
South Korea	72,724		62,215		63,011		56,793
France	67,657		62,146		53,672		49,293
China	57,567		56,060		54,415		43,088
Other EMEA	193,317		182,228		166,472		151,250
Other international	109,579		110,361		106,029		100,170
Total revenue	$	1,293,636	$	1,216,469	$	1,095,250	$	988,465

Property and equipment by geographic area is as follows:



	December 31,
(in thousands)	2018		2017
United States	$	46,605	$	45,498
India	4,176		3,704
EMEA	7,120		5,114
Other international	3,754		2,780
Total property and equipment, net	$	61,655	$	57,096

Unconditional Purchase Obligations

12 Months Ended

Dec. 31, 2018

Unconditional Purchase Obligations (Excluding Capital Stock Redemptions) [Abstract]

Unconditional Purchase Obligations

The Company has entered into various unconditional purchase obligations which primarily include royalties, software licenses and long-term purchase contracts for network, communication and office maintenance services. The Company expended $22.4 million, $14.1 million and $7.2 million related to unconditional purchase obligations that existed as of the beginning of each year for the years ended December 31, 2018, 2017 and 2016, respectively. Future expenditures under unconditional purchase obligations in effect as of December 31, 2018 are as follows:



(in thousands)
2019	$	24,182
2020	8,588
2021	4,633
2022	54
2023	54
Total	$	37,511

Restructuring

12 Months Ended

Dec. 31, 2018

Restructuring and Related Activities [Abstract]

Restructuring

During the fourth quarter of 2016, the Company initiated workforce realignment activities to reallocate resources to align with the Company's future strategic plans. The Company completed the workforce realignment activities as of September 30, 2017. The Company incurred related restructuring charges as follows:



(in thousands)	Gross		Net of Tax
Q4 2016	$	3,419	$	2,355
Q1 2017	9,273		6,176
Q2 2017	2,000		1,435
Q3 2017	466		331
Total restructuring charges	$	15,158	$	10,297

The restructuring charges are included in the presentation of cost of software licenses; cost of maintenance and service; research and development expense; and selling, general and administrative expense. The gross charges were fully paid as of March 31, 2018.

Contingencies and Commitments	12 Months Ended
Contingencies and Commitments	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Commitments	Contingencies and Commitments The Company is subject to various investigations, claims and legal proceedings that arise in the ordinary course of business, including commercial disputes, labor and employment matters, tax audits, alleged infringement of intellectual property rights and other matters. In the opinion of the Company, the resolution of pending matters is not expected to have a material adverse effect on the Company's consolidated results of operations, cash flows or financial position. However, each of these matters is subject to various uncertainties and it is possible that an unfavorable resolution of one or more of these proceedings could materially affect the Company's results of operations, cash flows or financial position. An Indian subsidiary of the Company has several service tax audits pending that have resulted in formal inquiries being received on transactions through mid-2012. The Company could incur tax charges and related liabilities of approximately $7.1 million. The service tax issues raised in the Company’s notices and inquiries are very similar to the case, M/s Microsoft Corporation (I) (P) Ltd. Vs. Commissioner of Service Tax, New Delhi, wherein the Delhi Customs, Excise and Service Tax Appellate Tribunal (CESTAT) passed a favorable ruling to Microsoft. The Company can provide no assurances on whether the Microsoft case's favorable ruling will be challenged in higher courts or on the impact that the present Microsoft case’s decision will have on the Company’s cases. The Company is uncertain as to when these service tax matters will be concluded. The Company sells software licenses and services to its customers under proprietary software license agreements. Each license agreement contains the relevant terms of the contractual arrangement with the customer, and generally includes certain provisions for indemnifying the customer against losses, expenses and liabilities from damages that are incurred by or awarded against the customer in the event the Company's software or services are found to infringe upon a patent, copyright or other proprietary right of a third party. To date, the Company has not had to reimburse any of its customers for any losses related to these indemnification provisions and no material claims asserted under these indemnification provisions are outstanding as of December 31, 2018. For several reasons, including the lack of prior material indemnification claims, the Company cannot determine the maximum amount of potential future payments, if any, related to such indemnification provisions.

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Acquisitions In February 2019, the Company acquired 100% of the shares of Granta Design Limited (Granta Design) and Helic, Inc. (Helic) for a combined purchase price of approximately $261.5 million. The acquisition of Granta Design, the premier provider of materials information technology, expands the Company's portfolio into this important area, giving customers access to material intelligence, including data that is critical to successful simulations. The acquisition of Helic, the industry-leading provider of electromagnetic crosstalk solutions for systems on chips, combined with the Company's flagship electromagnetic and semiconductor solvers, will provide a comprehensive solution for on-chip, 3D integrated circuit and chip-package-system electromagnetics and noise analysis. Credit Facility Also in February 2019, the Company entered into a $500 million unsecured revolving credit facility. The revolving credit facility will be available for general corporate purposes, including, among others, to finance acquisitions, share repurchases and capital expenditures, and becomes payable in full in February 2024.

Schedule II - Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2018

SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]

Valuation and Qualifying Accounts

ANSYS, INC. AND SUBSIDIARIES

Valuation and Qualifying Accounts



(in thousands) Description	Balance at Beginning of Year		Additions: Charges to Costs and Expenses		Deductions: Returns and Write-Offs		Balance at End of Year
Year ended December 31, 2018 Allowance for doubtful accounts	$	6,800	$	1,577	$	377	$	8,000
Year ended December 31, 2017 Allowance for doubtful accounts	$	5,700	$	1,474	$	374	$	6,800
Year ended December 31, 2016 Allowance for doubtful accounts	$	5,200	$	2,009	$	1,509	$	5,700

Summary Of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Accounting Principles

Principles Of Consolidation

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated.

Recently Adopted Accounting Guidance

Accounting Guidance Issued And Not Yet Adopted

Accounting Guidance Issued and Not Yet Adopted

Use Of Estimates

Use of Estimates


•	Allowances for doubtful accounts receivable


•	Income tax accruals, including those related to the Tax Cuts and Jobs Act


•	Uncertain tax positions


•	Tax valuation reserves


•	Fair value of stock-based compensation and probabilities of performance award attainment


•	Contract revenue


•	Acquired deferred revenue


•	Useful lives for depreciation and amortization


•	Valuations of goodwill and other intangible assets


•	Deferred compensation


•	Loss contingencies

Actual results could differ from these estimates. Changes in estimates are recorded in the results of operations in the period that the changes occur.

Revenue Recognition

Revenue Recognition Policy 2018 (ASC 606)

Significant Judgments (ASC 606)

Revenue Recognition Policy 2017 and 2016 (ASC 605)

Cash And Cash Equivalents

Cash and Cash Equivalents



	December 31, 2018			December 31, 2017
(in thousands, except percentages)	Amount		% of Total	Amount		% of Total
Cash accounts	$	331,084	42.6	$	568,587	64.5
Money market funds	446,055		57.4	312,914		35.5
Total	$	777,139		$	881,501

The Company's money market fund balances are held in various funds of a single issuer.

Property And Equipment

Property and Equipment

Research And Development

Research and Development

Business Combinations

Goodwill And Other Intangible Assets

Goodwill and Other Intangible Assets

Concentrations Of Credit Risk

Concentrations of Credit Risk



	Year Ended December 31,
(as a % of revenue)	2018		2017		2016
Revenue from channel partners	22	%	25	%	24	%
Largest channel partner	4	%	5	%	5	%
2^nd largest channel partner	2	%	2	%	2	%

No single customer accounted for more than 5% of the Company's revenue in 2018, 2017 or 2016.



	As of December 31,
(in thousands)	2018		2017
Cash and cash equivalents held domestically	$	616,249	$	561,417
Cash and cash equivalents held by foreign subsidiaries	160,890		320,084
Cash and cash equivalents held in excess of deposit insurance, foreign and domestic	754,163		852,138
Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic	452,166		328,902

Allowance For Doubtful Accounts

Allowance for Doubtful Accounts

Income Taxes

Foreign Currencies

Accumulated Other Comprehensive Loss

Accumulated other comprehensive loss is composed entirely of foreign currency translation adjustments.

Earnings Per Share

The details of basic and diluted EPS are as follows:



	Year Ended December 31,
(in thousands, except per share data)	2018		2017		2016
Net income	$	419,375	$	259,251	$	265,636
Weighted average shares outstanding – basic	83,973		84,988		87,227
Dilutive effect of stock plans	1,940		1,866		1,742
Weighted average shares outstanding – diluted	85,913		86,854		88,969
Basic earnings per share	$	4.99	$	3.05	$	3.05
Diluted earnings per share	$	4.88	$	2.98	$	2.99
Anti-dilutive shares	7		84		260

Stock-Based Compensation

Fair Value Of Financial Instruments

Fair Value of Financial Instruments

Summary Of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Summary Of Cash And Cash Equivalents

The Company's cash and cash equivalents balances comprise the following:



	December 31, 2018			December 31, 2017
(in thousands, except percentages)	Amount		% of Total	Amount		% of Total
Cash accounts	$	331,084	42.6	$	568,587	64.5
Money market funds	446,055		57.4	312,914		35.5
Total	$	777,139		$	881,501

Basic And Diluted Earnings Per Share

The details of basic and diluted EPS are as follows:



	Year Ended December 31,
(in thousands, except per share data)	2018		2017		2016
Net income	$	419,375	$	259,251	$	265,636
Weighted average shares outstanding – basic	83,973		84,988		87,227
Dilutive effect of stock plans	1,940		1,866		1,742
Weighted average shares outstanding – diluted	85,913		86,854		88,969
Basic earnings per share	$	4.99	$	3.05	$	3.05
Diluted earnings per share	$	4.88	$	2.98	$	2.99
Anti-dilutive shares	7		84		260

Customer Concentration Risk

Schedule Of Risk Concentration

The following table outlines concentrations of risk with respect to the Company's revenue:



	Year Ended December 31,
(as a % of revenue)	2018		2017		2016
Revenue from channel partners	22	%	25	%	24	%
Largest channel partner	4	%	5	%	5	%
2^nd largest channel partner	2	%	2	%	2	%

Credit Concentration Risk

Schedule Of Risk Concentration

The following table outlines concentrations of risk with respect to the Company's cash and cash equivalents:



	As of December 31,
(in thousands)	2018		2017
Cash and cash equivalents held domestically	$	616,249	$	561,417
Cash and cash equivalents held by foreign subsidiaries	160,890		320,084
Cash and cash equivalents held in excess of deposit insurance, foreign and domestic	754,163		852,138
Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic	452,166		328,902

Revenue from Contracts with Customers (Tables)

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Impact of ASC 606 on Condensed Consolidated Financial Statement Line Items

The following table compares the impacted assets and liabilities on the consolidated balance sheet as of December 31, 2018 to the amounts had ASC 605 been in effect:



	December 31, 2018
(in thousands)	As Reported (ASC 606)		ASC 605		Change
Accounts receivable, less allowance for doubtful accounts of $8,000	$	317,700	$	135,190	$	182,510
Other receivables and current assets	216,113		351,246		(135,133		)
Other long-term assets	82,775		43,429		39,346
Deferred income tax assets	26,630		65,973		(39,343		)
Accrued income taxes	8,726		—		8,726
Other accrued expenses and liabilities	99,559		101,949		(2,390		)
Deferred revenue - current	328,584		526,168		(197,584		)
Deferred income tax liabilities	30,077		23,056		7,021
Other long-term liabilities	61,573		76,354		(14,781		)
Stockholders' equity	$	2,649,547	$	2,403,159	$	246,388

The following table compares the impacted amounts on the consolidated statements of income for the year ended December 31, 2018 to the amounts had ASC 605 been in effect:



(in thousands, except per share data)	As Reported (ASC 606)		ASC 605		Change
Revenue:
Software licenses	$	576,717	$	676,846	$	(100,129	)
Maintenance and service	716,919		539,623		177,296
Cost of sales:
Software licenses	18,619		36,852		(18,233		)
Maintenance and service	110,232		91,999		18,233
Income tax provision	67,710		53,067		14,643
Earnings per share:
Basic	$	4.99	$	4.25	$	0.74
Diluted	$	4.88	$	4.15	$	0.73

Disaggregation of Revenue

The following table summarizes revenue for the years ended December 31, 2018, 2017 and 2016:



	Year Ended December 31,
(in thousands)	2018 (ASC 606)		2018 (ASC 605)		2017 (ASC 605)		2016 (ASC 605)
Revenue:
Lease licenses	$	275,619	$	421,268	$	376,886	$	340,331
Perpetual licenses	301,098		255,578		248,078		227,843
Software licenses	576,717		676,846		624,964		568,174
Maintenance	676,883		499,510		440,428		394,745
Service	40,036		40,113		29,858		25,546
Maintenance and service	716,919		539,623		470,286		420,291
Total revenue	$	1,293,636	$	1,216,469	$	1,095,250	$	988,465

Changes in Deferred Revenue

The changes in deferred revenue during the year ended December 31, 2018, inclusive of both current and long-term, are as follows:



(in thousands)
Beginning balance – January 1	$	299,730
Acquired deferred revenue	2,470
Recognition of deferred revenue	(1,293,636		)
Deferral of revenue	1,339,964
Currency translation	(5,354		)
Ending balance – December 31	$	343,174

Remaining Performance Obligations, Expected Timing of Satisfaction

Total revenue allocated to remaining performance obligations was $659.2 million as of December 31, 2018 and will be recognized as revenue as follows:



(in thousands)
Next 12 months	$	475,883
Months 13-24	125,048
Months 25-36	43,470
Thereafter	14,771
Total revenue allocated to remaining performance obligations	$	659,172

Acquisitions (Tables)

12 Months Ended

Dec. 31, 2018

Business Combinations [Abstract]

Schedule of Consideration Transferred

Fair Value of Consideration Transferred:



(in thousands)
Cash	$	290,983

Schedule of Recognized Identified Assets Acquired and Liabilities Assumed

Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed:



(in thousands)
Cash	$	7,957
Accounts receivable and other tangible assets	15,979
Developed software and core technologies (9 – 10 year life)	47,597
Customer lists (12 year life)	41,303
Trade names (4 – 10 year life)	10,749
Accounts payable and other liabilities	(11,444		)
Deferred revenue	(2,470		)
Net deferred tax liabilities	(23,187		)
Total identifiable net assets	$	86,484
Goodwill	$	204,499

Business Acquisition, Pro Forma Information

The table presented below reflects the impact of OPTIS from the date of acquisition to December 31, 2018. The operating loss does not include integration costs borne directly by ANSYS, Inc. and its non-OPTIS subsidiaries as a result of the acquisition.



	Year Ended December 31, 2018
(in thousands)	ASC 606			ASC 605
Revenue	$	18,532		$	12,276
Operating loss	$	(5,462	)	$	(11,718	)

Receivables and Other Current Assets (Tables)

12 Months Ended

Dec. 31, 2018

Prepaid Expense and Other Assets, Current [Abstract]

Schedule of Receivables and Other Current Assets

The Company's receivables and other current assets comprise the following balances:



	December 31,
(in thousands)	2018		2017
Accounts receivable, less allowance for doubtful accounts of $8,000 and $6,800, respectively	$	317,700	$	124,659

Receivables related to unrecognized revenue	$	167,144	$	215,155
Income taxes receivable, including overpayments and refunds	13,709		21,663
Prepaid expenses and other current assets	35,260		27,002
Total other receivables and current assets	$	216,113	$	263,820

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Components Of Property and Equipment

Property and equipment consists of the following:



		December 31,
(in thousands)	Estimated Useful Lives	2018			2017
Equipment	1-12 years	$	92,409		$	88,189
Computer software	1-5 years	35,053			34,994
Buildings and improvements	5-40 years	27,352			26,423
Leasehold improvements	1-17 years	15,782			13,316
Furniture	1-13 years	10,846			9,239
Land		1,759			1,759
Property and equipment, gross		183,201			173,920
Less: Accumulated depreciation		(121,546		)	(116,824		)
Property and equipment, net		$	61,655		$	57,096

Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets and Estimated Useful Lives

The Company's intangible assets and estimated useful lives are classified as follows:



	December 31, 2018					December 31, 2017
(in thousands)	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
Finite-lived intangible assets:
Developed software and core technologies (3 – 11 years)	$	410,680	$	(314,730	)	$	365,317	$	(297,645	)
Customer lists and contract backlog (5 – 15 years)	209,031		(117,614		)	171,048		(104,522		)
Trade names (2 – 10 years)	137,225		(113,677		)	127,200		(104,130		)
Total	$	756,936	$	(546,021	)	$	663,565	$	(506,297	)
Indefinite-lived intangible assets:
Trade name	$	357				$	357

Estimated Future Amortization Expense for Intangible Assets

As of December 31, 2018, estimated future amortization expense for the intangible assets reflected above is as follows:



(in thousands)
2019	$	31,652
2020	32,723
2021	29,900
2022	26,182
2023	23,275
Thereafter	67,183
Total intangible assets subject to amortization, net	210,915
Indefinite-lived trade name	357
Other intangible assets, net	$	211,272

Changes in Goodwill

The changes in goodwill during the years ended December 31, 2018 and 2017 are as follows:



(in thousands)	2018			2017
Beginning balance - January 1	$	1,378,553		$	1,337,215
Acquisitions and adjustments⁽¹⁾	204,381			36,443
Currency translation	(10,479		)	4,895
Ending balance - December 31	$	1,572,455		$	1,378,553

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value of Assets and Liabilities Measured on Recurring Basis

The following tables provide the assets carried at fair value and measured on a recurring basis:



			Fair Value Measurements at Reporting Date Using:
(in thousands)	December 31, 2018		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents	$	446,055	$	446,055	$	—	$	—
Short-term investments	$	225	$	—	$	225	$	—
Deferred compensation plan investments	$	1,646	$	1,646	$	—	$	—



			Fair Value Measurements at Reporting Date Using:
(in thousands)	December 31, 2017		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents	$	312,914	$	312,914	$	—	$	—
Short-term investments	$	286	$	—	$	286	$	—
Deferred compensation plan investments	$	3,742	$	3,742	$	—	$	—

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Components Of Income Before Income Taxes

Income before income taxes includes the following components:



	Year Ended December 31,
(in thousands)	2018		2017		2016
Domestic	$	455,478	$	344,447	$	340,251
Foreign	31,607		51,247		40,064
Total	$	487,085	$	395,694	$	380,315

Components Of Provision For Income Taxes

The provision for income taxes is composed of the following:



	Year Ended December 31,
(in thousands)	2018			2017			2016
Current:
Federal	$	58,138		$	112,414		$	99,783
State	12,888			7,879			8,338
Foreign	30,359			18,843			17,479
Deferred:
Federal	(20,764		)	(7,387		)	(13,368		)
State	(2,901		)	(584		)	(1,036		)
Foreign	(10,010		)	5,278			3,483
Total	$	67,710		$	136,443		$	114,679

Reconciliation Of U.S. Federal Statutory Tax Rate To Consolidated Effective Tax Rate

The reconciliation of the U.S. federal statutory tax rate to the consolidated effective tax rate is as follows:



	Year Ended December 31,
	2018		2017		2016
Federal statutory tax rate	21.0	%	35.0	%	35.0	%
State income taxes, net of federal benefit	1.5		1.1		1.6
Foreign rate differential	0.8		0.1		0.1
Uncertain tax positions	0.5		0.3		(0.2	)
U.S. tax reform enactment	0.2		4.5		—
Domestic production activity benefit	—		(2.6	)	(3.7	)
Benefit from entity structuring activities	(1.4	)	—		(2.2	)
Research and development credits	(2.3	)	(1.4	)	(1.0	)
Stock-based compensation	(3.3	)	(3.1	)	0.2
Foreign-derived intangible income deduction	(3.9	)	—		—
Other	0.8		0.6		0.4
	13.9	%	34.5	%	30.2	%

Components Of Deferred Tax Assets And Liabilities

The components of deferred tax assets and liabilities are as follows:



	December 31,
(in thousands)	2018			2017
Deferred tax assets:
Stock-based compensation	$	20,464		$	17,825
Net operating loss carryforwards	19,741			21,391
Uncertain tax positions	17,823			15,424
Employee benefits	15,048			8,603
Research and development credits	5,951			3,699
Allowance for doubtful accounts	1,616			1,462
Deferred revenue	—			5,134
Other	2,505			2,003
Valuation allowance	(2,127		)	(1,906		)
	81,021			73,635
Deferred tax liabilities:
Other intangible assets	(38,787		)	(29,924		)
Accounting method change	(31,626		)	—
Deferred revenue	(12,021		)	—
Property and equipment	(2,034		)	(1,557		)
Unremitted foreign earnings	—			(1,504		)
	(84,468		)	(32,985		)
Net deferred tax (liabilities) assets	$	(3,447	)	$	40,650

Reconciliation Of Unrecognized Tax Benefits

The following is a reconciliation of the total amounts of unrecognized tax benefits:



	Year Ended December 31,
(in thousands)	2018			2017			2016
Unrecognized tax benefit as of January 1	$	19,657		$	15,209		$	16,067
Gross increases—tax positions in prior period	1,229			905			983
Gross decreases—tax positions in prior period	(376		)	(765		)	(2,502		)
Gross increases—tax positions in current period	4,014			3,757			2,725
Reductions due to a lapse of the applicable statute of limitations	(994		)	(847		)	(927		)
Changes due to currency fluctuation	(703		)	1,414			(348		)
Settlements	—			(16		)	(789		)
Unrecognized tax benefit as of December 31	$	22,827		$	19,657		$	15,209

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Stock-Based Compensation Expense

Total stock-based compensation expense recognized for the years ended December 31, 2018, 2017 and 2016 is as follows:



	Year Ended December 31,
(in thousands, except per share amounts)	2018			2017			2016
Cost of sales:
Software licenses	$	—		$	969		$	701
Maintenance and service	5,224			2,533			1,578
Operating expenses:
Selling, general and administrative	47,099			30,817			15,990
Research and development	31,023			18,835			15,078
Stock-based compensation expense before taxes	83,346			53,154			33,347
Related income tax benefits	(34,518		)	(20,503		)	(10,538		)
Stock-based compensation expense, net of taxes	$	48,828		$	32,651		$	22,809
Net impact on earnings per share:
Basic earnings per share	$	(0.58	)	$	(0.38	)	$	(0.26	)
Diluted earnings per share	$	(0.57	)	$	(0.38	)	$	(0.26	)

Summary Of Stock Options

Information regarding stock option transactions is summarized below:



	Year Ended December 31,
	2018				2017				2016
(options in thousands)	Options		Weighted- Average Exercise Price		Options		Weighted- Average Exercise Price		Options		Weighted- Average Exercise Price
Outstanding, beginning of year	2,170		$	59.17	3,136		$	56.37	3,986		$	51.07
Granted	—		$	—	—		$	—	260		$	94.38
Exercised	(679	)	$	50.92	(956	)	$	49.78	(1,082	)	$	45.57
Forfeited	(7	)	$	86.28	(10	)	$	80.92	(28	)	$	72.07
Outstanding, end of year	1,484		$	62.80	2,170		$	59.17	3,136		$	56.37
Vested and Exercisable, end of year	1,347		$	59.69	1,930		$	55.11	2,762		$	51.80
Nonvested	137		$	93.44	240		$	91.71	374		$	90.12



	2018		2017		2016
Weighted Average Remaining Contractual Term (in years)
Outstanding	3.55		4.10		4.62
Vested and Exercisable	3.14		3.57		4.04
Nonvested	7.60		8.30		8.93
Aggregate Intrinsic Value (in thousands)
Exercised	$	78,648	$	58,472	$	49,752
Outstanding	$	118,908	$	191,895	$	113,822
Vested and Exercisable	$	112,133	$	178,456	$	112,379
Nonvested	$	6,775	$	13,439	$	1,443
Compensation Expense - Stock Options (in thousands)	$	2,006	$	2,948	$	7,406

Summary Of Restricted Stock Units

Information regarding all employee RSU transactions is summarized below:



	Year Ended December 31,
	2018				2017				2016
(RSUs in thousands)	RSUs		Weighted- Average Grant Date Fair Value		RSUs		Weighted- Average Grant Date Fair Value		RSUs		Weighted- Average Grant Date Fair Value
Nonvested, beginning of year	1,361		$	100.66	906		$	86.45	656		$	83.30
Granted⁽¹⁾	681		$	163.67	866		$	109.67	588		$	87.50
Performance adjustment⁽²⁾	76		$	151.52	35		$	98.29	(90	)	$	77.68
Vested	(524	)	$	101.38	(341	)	$	88.58	(176	)	$	83.79
Forfeited	(72	)	$	125.29	(105	)	$	90.80	(72	)	$	83.82
Nonvested, end of year	1,522		$	129.96	1,361		$	100.66	906		$	86.45

Summary Of Deferred Stock Awards To Non-Employee Directors

Information regarding deferred stock awards to non-employee Directors is summarized below:



	Year Ended December 31, 2018
	Diversified		Undiversified		Total
Deferred Awards Outstanding, beginning of year	29,500		159,599		189,099
Shares Diversified	6,105		(6,105	)	—
Shares Issued Upon Retirement	(23,355	)	(33,045	)	(56,400	)
Deferred Awards Outstanding, end of year	12,250		120,449		132,699

Employee Stock Option

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Assumptions To Estimate Fair Value Of Stock Awards

The table below presents the weighted average input assumptions used and resulting fair values for options granted or issued in business combinations during the year ended December 31, 2016:



Risk-free interest rate	1.19% to 1.93%
Expected dividend yield	—%
Expected volatility	24%
Expected term	5.7 years
Weighted average fair value per share	$23.96

Information Regarding Stock Options Outstanding

Information regarding stock options outstanding as of December 31, 2018 is summarized below:



(options in thousands)	Options Outstanding				Options Exercisable				Options Unvested
Range of Exercise Prices	Options	Weighted- Average Remaining Contractual Life (years)	Weighted- Average Exercise Price		Options	Weighted- Average Remaining Contractual Life (years)	Weighted- Average Exercise Price		Options	Weighted- Average Remaining Contractual Life (years)	Weighted- Average Exercise Price
$5.91 - $48.97	458	1.57	$	42.12	457	1.56	$	42.20	1	6.00	$	12.26
$58.67	359	2.84	$	58.67	359	2.84	$	58.67	—	0.00	$	—
$61.68 - $65.72	11	0.44	$	63.75	11	0.44	$	63.75	—	0.00	$	—
$67.44 - $95.09	656	5.38	$	79.50	520	4.79	$	75.68	136	7.61	$	94.16

Restricted Stock Units (RSUs) [Member]

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Assumptions To Estimate Fair Value Of Stock Awards

The determination of the fair values of the awards was affected by the grant date and several variables, each of which has been identified in the chart below:



	Year Ended December 31,
Assumptions used in Monte Carlo lattice pricing model	2018	2017	2016
Risk-free interest rate	2.4%	1.5%	1.0%
Expected dividend yield	—%	—%	—%
Expected volatility—ANSYS stock price	21%	19%	21%
Expected volatility—Nasdaq Composite Index	15%	15%	16%
Expected term	2.8 years	2.8 years	2.8 years
Correlation factor	0.65	0.70	0.65
Weighted average fair value per share	191.76	120.94	78.71

Stock Repurchase Program (Tables)

12 Months Ended

Dec. 31, 2018

Class of Stock Disclosures [Abstract]

Stock Repurchase Program

Under the Company's stock repurchase program, the Company repurchased shares as follows:



	Year Ended December 31,
(in thousands, except per share data)	2018		2017		2016
Number of shares repurchased	1,674		2,750		3,700
Average price paid per share	$	161.12	$	122.20	$	90.90
Total cost	$	269,801	$	336,042	$	336,335

Leases (Tables)

12 Months Ended

Dec. 31, 2018

Leases [Abstract]

Schedule of Future Minimum Rental Payments for Operating Leases

Future minimum lease payments, including termination fees, under noncancellable operating leases for office space in effect at December 31, 2018 are as follows:



(in thousands)
2019	$	16,354
2020	12,469
2021	10,177
2022	8,523
2023	6,809
Thereafter	14,267
Total	$	68,599

Geographic Information (Tables)

12 Months Ended

Dec. 31, 2018

Segments, Geographical Areas [Abstract]

Revenue By Geographic Area

Revenue by geographic area is as follows:



	Year Ended December 31,
(in thousands)	2018 (ASC 606)		2018 (ASC 605)		2017 (ASC 605)		2016 (ASC 605)
United States	$	506,335	$	480,997	$	417,343	$	367,892
Japan	145,951		137,733		126,097		120,159
Germany	140,506		124,729		108,211		99,820
South Korea	72,724		62,215		63,011		56,793
France	67,657		62,146		53,672		49,293
China	57,567		56,060		54,415		43,088
Other EMEA	193,317		182,228		166,472		151,250
Other international	109,579		110,361		106,029		100,170
Total revenue	$	1,293,636	$	1,216,469	$	1,095,250	$	988,465

Property and Equipment by Geographic Area

Property and equipment by geographic area is as follows:



	December 31,
(in thousands)	2018		2017
United States	$	46,605	$	45,498
India	4,176		3,704
EMEA	7,120		5,114
Other international	3,754		2,780
Total property and equipment, net	$	61,655	$	57,096

Unconditional Purchase Obligations (Tables)

12 Months Ended

Dec. 31, 2018

Unconditional Purchase Obligations (Excluding Capital Stock Redemptions) [Abstract]

Unrecorded Unconditional Purchase Obligations Disclosure

Future expenditures under unconditional purchase obligations in effect as of December 31, 2018 are as follows:



(in thousands)
2019	$	24,182
2020	8,588
2021	4,633
2022	54
2023	54
Total	$	37,511

Restructuring (Tables)

12 Months Ended

Dec. 31, 2018

Restructuring and Related Activities [Abstract]

Restructuring and Related Costs

The Company incurred related restructuring charges as follows:



(in thousands)	Gross		Net of Tax
Q4 2016	$	3,419	$	2,355
Q1 2017	9,273		6,176
Q2 2017	2,000		1,435
Q3 2017	466		331
Total restructuring charges	$	15,158	$	10,297

Organization - Additional Information (Detail)	12 Months Ended
Organization - Additional Information (Detail)	Dec. 31, 2018 Segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	1

Summary Of Significant Accounting Policies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2018 USD ($)
Cumulative effect of new accounting principle in period of adoption		$ 183,120		$ 183,100
Lease license to license revenue	50.00%
Lease license to maintenance revenue	50.00%
Amortization	$ 40,829	49,766	$ 50,847
Provisions for doubtful accounts	1,577	1,474	2,009
Net foreign exchange (losses) gains	(3,058)	$ (1,935)	$ 77
Minimum
Cumulative effect of new accounting principle in period of adoption	$ 80,000
Semiconductor product licenses, term		24 months
Property and equipment, estimated useful lives (years)	1 year
Maximum
Cumulative effect of new accounting principle in period of adoption	$ 100,000
Semiconductor product licenses, term		36 months
Property and equipment, estimated useful lives (years)	40 years
Customer Concentration Risk
Number of customers with more than five percent of revenue	0	0	0

Summary Of Significant Accounting Policies (Summary Of Cash And Cash Equivalents) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Cash accounts	$ 331,084	$ 568,587
Money market funds	446,055	312,914
Cash and cash equivalents	$ 777,139	$ 881,501	$ 822,479	$ 784,168
Cash accounts, % of Total	42.60%	64.50%
Money market funds, % of Total	57.40%	35.50%

Summary Of Significant Accounting Policies (Schedule Of Risk Concentration) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration Risk [Line Items]
Cash and cash equivalents, at carrying value	$ 777,139	$ 881,501	$ 822,479	$ 784,168
Customer Concentration Risk
Concentration Risk [Line Items]
Channel partner concentration risk, percentage	22.40%	24.70%	24.40%
Credit Concentration Risk
Concentration Risk [Line Items]
Cash and cash equivalents held in excess of deposit insurance, foreign and domestic	$ 754,163	$ 852,138
Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic	$ 452,166	$ 328,902
1st Largest Channel Partner [Member] \| Customer Concentration Risk
Concentration Risk [Line Items]
Channel partner concentration risk, percentage	4.00%	5.00%	5.00%
2nd Largest Channel Partner [Member] \| Customer Concentration Risk
Concentration Risk [Line Items]
Channel partner concentration risk, percentage	2.00%	2.00%	2.00%
United States \| Credit Concentration Risk
Concentration Risk [Line Items]
Cash and cash equivalents, at carrying value	$ 616,249	$ 561,417
FOREIGN \| Credit Concentration Risk
Concentration Risk [Line Items]
Cash and cash equivalents, at carrying value	$ 160,890	$ 320,084

Summary Of Significant Accounting Policies (Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Net income	$ 419,375	$ 259,251	$ 265,636
Weighted average shares outstanding - basic	83,973	84,988	87,227
Dilutive effect of stock plans	1,940	1,866	1,742
Weighted average shares outstanding - diluted	85,913	86,854	88,969
Basic earnings per share	$ 4.99	$ 3.05	$ 3.05
Diluted earnings per share	$ 4.88	$ 2.98	$ 2.99
Anti-dilutive shares	7	84	260

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Revenue from Contracts with Customers - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Total revenue	$ 1,293,636	$ 1,095,250	$ 988,465
Cumulative effect of new accounting principle in period of adoption		$ 183,120		$ 183,100
Lease license to license revenue	50.00%
2018 tax payments related to the adoption of ASC 606	$ 14,000
Amount of revenue recognized from beginning deferred revenue and backlog	387,200
Revenue, remaining performance obligation, amount	659,172
Gross impact
Cumulative effect of new accounting principle in period of adoption				242,400
Deferred Revenue
Cumulative effect of new accounting principle in period of adoption				$ 244,100
Calculated under Revenue Guidance in Effect before Topic 606
Total revenue	$ 1,216,469

Impact of ASC 606 on Condensed Consolidated Financial Statement Line Items (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts receivable, less allowance for doubtful accounts of $8,000	$ 317,700	$ 124,659
Other receivables and current assets	216,113	263,820
Other long-term assets	82,775	35,972
Deferred income tax assets	26,630	42,111
Accrued income taxes	8,726	5,760
Other accrued expenses and liabilities	99,559	86,335
Deferred revenue - current	328,584	440,491
Deferred income tax liabilities	30,077	1,461
Other long-term liabilities	61,573	85,778
Stockholders' equity	2,649,547	2,245,831	$ 2,208,405	$ 2,194,427
Total revenue	1,293,636	1,095,250	988,465
Cost of goods and services sold	155,885	150,164	146,860
Income tax provision	$ 67,710	$ 136,443	$ 114,679
Basic earnings per share	$ 4.99	$ 3.05	$ 3.05
Diluted earnings per share	$ 4.88	$ 2.98	$ 2.99
Accounting Standards Update 2014-09
Accounts receivable, less allowance for doubtful accounts of $8,000	$ 182,510
Other receivables and current assets	(135,133)
Other long-term assets	39,346
Deferred income tax assets	(39,343)
Accrued income taxes	8,726
Other accrued expenses and liabilities	(2,390)
Deferred revenue - current	(197,584)
Deferred income tax liabilities	7,021
Other long-term liabilities	(14,781)
Stockholders' equity	246,388
Income tax provision	$ 14,643
Basic earnings per share	$ 0.74
Diluted earnings per share	$ 0.73
Software licenses
Total revenue	$ 576,717	$ 624,964	$ 568,174
Cost of goods and services sold	18,619	34,421	28,860
Software licenses \| Accounting Standards Update 2014-09
Total revenue	(100,129)
Cost of goods and services sold	(18,233)
Maintenance and service
Total revenue	716,919	470,286	420,291
Cost of goods and services sold	110,232	$ 78,949	$ 79,908
Maintenance and service \| Accounting Standards Update 2014-09
Total revenue	177,296
Cost of goods and services sold	18,233
Calculated under Revenue Guidance in Effect before Topic 606
Accounts receivable, less allowance for doubtful accounts of $8,000	135,190
Other receivables and current assets	351,246
Other long-term assets	43,429
Deferred income tax assets	65,973
Accrued income taxes	0
Other accrued expenses and liabilities	101,949
Deferred revenue - current	526,168
Deferred income tax liabilities	23,056
Other long-term liabilities	76,354
Stockholders' equity	2,403,159
Total revenue	1,216,469
Income tax provision	$ 53,067
Basic earnings per share	$ 4.25
Diluted earnings per share	$ 4.15
Calculated under Revenue Guidance in Effect before Topic 606 \| Software licenses
Total revenue	$ 676,846
Cost of goods and services sold	36,852
Calculated under Revenue Guidance in Effect before Topic 606 \| Maintenance and service
Total revenue	539,623
Cost of goods and services sold	$ 91,999

Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Total revenue	$ 1,293,636	$ 1,095,250	$ 988,465
Indirect sales channel revenue	22.40%	24.80%	24.40%
Lease license
Total revenue	$ 275,619	$ 376,886	$ 340,331
Perpetual license
Total revenue	301,098	248,078	227,843
Software licenses
Total revenue	576,717	624,964	568,174
Maintenance
Total revenue	676,883	440,428	394,745
Service
Total revenue	40,036	29,858	25,546
Maintenance and service
Total revenue	716,919	$ 470,286	$ 420,291
Accounting Standards Update 2014-09 \| Software licenses
Total revenue	(100,129)
Accounting Standards Update 2014-09 \| Maintenance and service
Total revenue	177,296
Calculated under Revenue Guidance in Effect before Topic 606
Total revenue	$ 1,216,469
Indirect sales channel revenue	23.46%
Calculated under Revenue Guidance in Effect before Topic 606 \| Lease license
Total revenue	$ 421,268
Calculated under Revenue Guidance in Effect before Topic 606 \| Perpetual license
Total revenue	255,578
Calculated under Revenue Guidance in Effect before Topic 606 \| Software licenses
Total revenue	676,846
Calculated under Revenue Guidance in Effect before Topic 606 \| Maintenance
Total revenue	499,510
Calculated under Revenue Guidance in Effect before Topic 606 \| Service
Total revenue	40,113
Calculated under Revenue Guidance in Effect before Topic 606 \| Maintenance and service
Total revenue	$ 539,623

Changes in Deferred Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	May 02, 2018
Movement in Deferred Revenue [Roll Forward]
Acquired deferred revenue				$ 2,470
Recognition of deferred revenue	$ (1,293,636)	$ (1,095,250)	$ (988,465)
Deferral of revenue	1,339,964
Currency translation	(5,354)
Ending balance	343,174
Balance at January 1st after ASC 606 Adoption
Movement in Deferred Revenue [Roll Forward]
Beginning balance	$ 299,730
Ending balance		$ 299,730

Remaining Performance Obligations, Expected Timing of Satisfaction (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 659,172
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 475,883
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 125,048
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 43,470
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, amount	$ 14,771
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	0 months

Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	May 02, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred revenue	$ 2,470
OPTIS
Percentage of shares acquired	100.00%
Business combination, consideration transferred	$ 290,983
Goodwill, period increase (decrease)		$ 1,800
Business combination, historical carrying value of acquired deferred revenue	14,200
Deferred revenue	2,470
Contract with customer, liability, increase (decrease) for contract acquired in business combination		8,700
Business acquisition write down of deferred revenue expected impact on revenue for fiscal year		1,600
Series of Individually Immaterial Business Acquisitions
Business combination, consideration transferred			$ 67,000	$ 10,300
Contract with customer, liability, increase (decrease) for contract acquired in business combination		700	$ 2,900	$ 100
Business acquisition write down of deferred revenue expected impact on revenue for fiscal year		100
Previous Accounting Guidance \| OPTIS
Business combination, historical carrying value of acquired deferred revenue	$ 22,300
Contract with customer, liability, increase (decrease) for contract acquired in business combination		14,400
Previous Accounting Guidance \| Series of Individually Immaterial Business Acquisitions
Contract with customer, liability, increase (decrease) for contract acquired in business combination		$ 1,200

Fair Value of Consideration Transferred (Details) $ in Thousands	May 02, 2018 USD ($)
OPTIS
Cash	$ 290,983

Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2018	May 02, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Combination, Separately Recognized Transactions [Line Items]
Deferred revenue		$ (2,470)
Goodwill	$ 1,572,455		$ 1,378,553	$ 1,337,215
OPTIS
Business Combination, Separately Recognized Transactions [Line Items]
Cash		7,957
Accounts receivable and other tangible assets		15,979
Accounts payable and other liabilities		(11,444)
Deferred revenue		(2,470)
Net deferred tax liabilities		(23,187)
Total identifiable net assets		86,484
Goodwill		204,499
OPTIS \| Developed Software and Core Technologies
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible assets		47,597
OPTIS \| Customer Lists and Contract Backlog
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible assets		41,303
OPTIS \| Trade Names
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible assets		$ 10,749

Estimated Useful Lives (Details)		12 Months Ended
Estimated Useful Lives (Details)	May 02, 2018	Dec. 31, 2018
Minimum \| Developed Software and Core Technologies
Finite-lived intangible asset, useful life		3 years
Minimum \| Customer Lists and Contract Backlog
Finite-lived intangible asset, useful life		5 years
Minimum \| Trade Names
Finite-lived intangible asset, useful life		2 years
Maximum \| Developed Software and Core Technologies
Finite-lived intangible asset, useful life		11 years
Maximum \| Customer Lists and Contract Backlog
Finite-lived intangible asset, useful life		15 years
Maximum \| Trade Names
Finite-lived intangible asset, useful life		10 years
OPTIS \| Customer Lists and Contract Backlog
Finite-lived intangible asset, useful life	12 years
OPTIS \| Minimum \| Developed Software and Core Technologies
Finite-lived intangible asset, useful life	9 years
OPTIS \| Minimum \| Trade Names
Finite-lived intangible asset, useful life	4 years
OPTIS \| Maximum \| Developed Software and Core Technologies
Finite-lived intangible asset, useful life	10 years
OPTIS \| Maximum \| Trade Names
Finite-lived intangible asset, useful life	10 years

Pro Forma Information (Details) - USD ($) $ in Thousands	12 Months Ended
Pro Forma Information (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues	$ 1,293,636	$ 1,095,250	$ 988,465
Operating income (loss)	476,574	$ 390,728	$ 376,242
OPTIS
Revenues	18,532
Operating income (loss)	(5,462)
Previous Accounting Guidance \| OPTIS
Revenues	12,276
Operating income (loss)	$ (11,718)

Schedule of Receivables and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Accounts receivable, less allowance for doubtful accounts of $8,000 and $6,800, respectively	$ 317,700		$ 124,659
Other receivables and current assets	216,113		263,820
Receivables related to unrecognized revenue
Other receivables and current assets	167,144		215,155
Income taxes receivable, including overpayments and refunds
Other receivables and current assets	13,709		21,663
Prepaid expenses and other current assets
Other receivables and current assets	$ 35,260		$ 27,002
Balance at January 1st after ASC 606 Adoption
Accounts receivable, less allowance for doubtful accounts of $8,000 and $6,800, respectively		$ 278,800
Balance at January 1st after ASC 606 Adoption \| Receivables related to unrecognized revenue
Other receivables and current assets		$ 136,400

Property and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Depreciation expense related to property and equipment	$ 18.4	$ 17.9	$ 18.7

Property and Equipment (Components Of Property and Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 183,201	$ 173,920
Less: Accumulated depreciation	(121,546)	(116,824)
Property and equipment, net	61,655	57,096
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	92,409	88,189
Computer Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	35,053	34,994
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	27,352	26,423
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	15,782	13,316
Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	10,846	9,239
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,759	$ 1,759
Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum \| Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum \| Computer Software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum \| Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	5 years
Minimum \| Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum \| Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	40 years
Maximum \| Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	12 years
Maximum \| Computer Software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	5 years
Maximum \| Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	40 years
Maximum \| Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	17 years
Maximum \| Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	13 years

Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	$ 756,936	$ 663,565
Amortized intangible assets, accumulated amortization	(546,021)	(506,297)
Unamortized intangible assets, gross carrying amount	357
Trade Names
Intangible Assets [Line Items]
Unamortized intangible assets, gross carrying amount	357	357
Developed Software and Core Technologies
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	410,680	365,317
Amortized intangible assets, accumulated amortization	(314,730)	(297,645)
Customer Lists and Contract Backlog
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	209,031	171,048
Amortized intangible assets, accumulated amortization	(117,614)	(104,522)
Trade Names
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	137,225	127,200
Amortized intangible assets, accumulated amortization	$ (113,677)	$ (104,130)

Estimated Useful Lives (Detail)	12 Months Ended
Estimated Useful Lives (Detail)	Dec. 31, 2018
Developed Software and Core Technologies \| Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	3 years
Developed Software and Core Technologies \| Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	11 years
Customer Lists and Contract Backlog \| Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	5 years
Customer Lists and Contract Backlog \| Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	15 years
Trade Names \| Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	2 years
Trade Names \| Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	10 years

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization	$ 40,829	$ 49,766	$ 50,847

Estimated Future Amortization Expense for Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
2019	$ 31,652
2020	32,723
2021	29,900
2022	26,182
2023	23,275
Thereafter	67,183
Total intangible assets subject to amortization, net	210,915
Indefinite-lived trade name	357
Other intangible assets, net	$ 211,272	$ 157,625

Changes in Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
Changes in Goodwill (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Beginning balance	$ 1,378,553	$ 1,337,215
Acquisitions and adjustments	204,381	36,443
Currency translation	(10,479)	4,895
Ending balance	$ 1,572,455	$ 1,378,553

Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 446,055	$ 312,914
Short-term investments	225	286
Deferred compensation plan investments	1,646	3,742
Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	446,055	312,914
Short-term investments	0	0
Deferred compensation plan investments	1,646	3,742
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Short-term investments	225	286
Deferred compensation plan investments	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Short-term investments	0	0
Deferred compensation plan investments	$ 0	$ 0

Fair Value Measurement - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments maturity	3 months
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments maturity	12 months

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended			15 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Income Tax Contingency [Line Items]
Federal statutory tax rate	21.00%	35.00%	35.00%
Effective income tax rate reconciliation, change in enacted tax rate, amount		$ 1,900
Effective income tax rate reconciliation, repatriation of foreign earnings, amount	$ 900	16,000		$ 16,900
Transition tax payment	15,600
Accrued income taxes, long-term	1,300			1,300
Foreign earnings repatriated	144,300
Effective income tax rate reconciliation, GILTI, amount	400
Deferred tax assets, operating loss carryforwards, foreign	19,500	25,200		19,500
Deferred tax assets, valuation allowance	2,127	1,906		2,127
Deferred tax assets, operating loss carryforwards, state and local	400			400
Tax credit carryforwards	4,300			4,300
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit	1,000			1,000
Unrecognized tax benefits that would impact effective tax rate	13,700			13,700
Penalty expense	800	1,100	$ 800
Interest (income) expense	(100)	400	$ 100
Liability for penalties	4,700	3,900		4,700
Liability for interest	4,000	3,600		4,000
Subject To Expiration [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	3,700			3,700
Subject To Utilization Limitations [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	2,200			2,200
Not Subject To Expiration [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	600			600
Foreign Country [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	73,800			73,800
Federal Domestic [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	5,600			5,600
Operating Loss Carryforward With No Expiration Date [Member] \| Foreign Country [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	46,000			46,000
Subject To Expiration [Member] \| Foreign Country [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 27,800			27,800
Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Tax credit carryforward, expiration date	Jan. 01, 2019
Years open to examination	2015
Earliest Tax Year [Member] \| Foreign Country [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Jan. 01, 2021
Earliest Tax Year [Member] \| Federal Domestic [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Jan. 01, 2025
Earliest Tax Year [Member] \| State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Jan. 01, 2029
Latest Tax Year [Member]
Income Tax Contingency [Line Items]
Tax credit carryforward, expiration date	Dec. 31, 2038
Years open to examination	2018
Latest Tax Year [Member] \| Foreign Country [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2035
Latest Tax Year [Member] \| Federal Domestic [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2036
Latest Tax Year [Member] \| State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2035
SEC Schedule, 12-09, Valuation Allowance, Operating Loss Carryforward [Member] \| Foreign Country [Member]
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance	$ 19,500	$ 25,200		$ 19,500
Maximum
Income Tax Contingency [Line Items]
Effective income tax rate reconciliation, deduction, percent	50.00%

Income Taxes (Components Of Income Before Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Domestic	$ 455,478	$ 344,447	$ 340,251
Foreign	31,607	51,247	40,064
Income before income tax provision	$ 487,085	$ 395,694	$ 380,315

Income Taxes (Components Of Provision For Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Current, Federal	$ 58,138	$ 112,414	$ 99,783
Current, State	12,888	7,879	8,338
Current, Foreign	30,359	18,843	17,479
Deferred, Federal	(20,764)	(7,387)	(13,368)
Deferred, State	(2,901)	(584)	(1,036)
Deferred, Foreign	(10,010)	5,278	3,483
Total	$ 67,710	$ 136,443	$ 114,679

Income Taxes (Reconciliation Of U.S. Federal Statutory Tax Rate To Consolidated Effective Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal statutory tax rate	21.00%	35.00%	35.00%
State income taxes, net of federal benefit	1.50%	1.10%	1.60%
Foreign rate differential	0.80%	0.10%	0.10%
Uncertain tax positions	0.50%	0.30%
Uncertain tax positions			(0.20%)
U.S. tax reform enactment	0.20%	4.50%	0.00%
Domestic production activity benefit	(0.00%)	(2.60%)	(3.70%)
Benefit from entity restructuring	(1.40%)	(0.00%)	(2.20%)
Research and development credits	(2.30%)	(1.40%)	(1.00%)
Stock-based compensation	(3.30%)	(3.10%)
Stock-based compensation			0.20%
Foreign-derived intangible income deduction	(3.90%)	(0.00%)	(0.00%)
Other	0.80%	0.60%	0.40%
Consolidated effective tax rate	13.90%	34.50%	30.20%

Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Stock-based compensation	$ 20,464	$ 17,825
Net operating loss carryforwards	19,741	21,391
Uncertain tax positions	17,823	15,424
Employee benefits	15,048	8,603
Research and development credits	5,951	3,699
Allowance for doubtful accounts	1,616	1,462
Deferred revenue	0	5,134
Other	2,505	2,003
Valuation allowance	(2,127)	(1,906)
Deferred tax assets	81,021	73,635
Other intangible assets	(38,787)	(29,924)
Accounting method change	(31,626)	0
Deferred revenue	(12,021)	0
Property and equipment	(2,034)	(1,557)
Unremitted foreign earnings	0	(1,504)
Deferred tax liabilities	(84,468)	(32,985)
Net deferred tax (liabilities) assets	$ (3,447)
Net deferred tax (liabilities) assets		$ 40,650

Income Taxes (Reconciliation Of Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefit as of January 1	$ 19,657	$ 15,209	$ 16,067
Gross increases-tax positions in prior period	1,229	905	983
Gross decreases-tax positions in prior period	(376)	(765)	(2,502)
Gross increases-tax positions in current period	4,014	3,757	2,725
Reductions due to a lapse of the applicable statute of limitations	(994)	(847)	(927)
Changes due to currency fluctuation		1,414
Changes due to currency fluctuation	(703)		(348)
Settlements	0	(16)	(789)
Unrecognized tax benefit as of December 31	$ 22,827	$ 19,657	$ 15,209

Pension And Profit-Sharing Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan Disclosure [Line Items]
Total unfunded portion of the defined benefit obligations	$ 9.7
Expenses related to retirement programs	$ 12.4	$ 10.1	$ 9.1
Four Zero One K Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Maximum annual contributions per employee, percent	4.25%
Minimum working hours per employee required to be eligible for discretionary contribution	1000 hours
First Three Percent Of Employee Pay [Member] \| Four Zero One K Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of employee contribution employer matches	100.00%
Percentage of employee pay employer matches	3.00%
More Than Three Percent Up To Eight Percent Of Employee Pay [Member] \| Four Zero One K Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of employee contribution employer matches	25.00%
Percentage of employee pay employer matches	5.00%

Stock-Based Compensation - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Restricted stock granted	681,000	866,000	588,000
Stock-based compensation expense	$ 83,346,000	$ 53,154,000	$ 33,347,000
Employee Stock Option
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares authorized for grant under the plan	39,800,000.0
Percentage of voting interest to be held by optionee	10.00%
Exercise price as a percentage of fair value at the time of grant	110.00%
Vesting period	4 years
Maximum months after sale event where awards fully vest when service relationship terminated without cause	18 months
Minimum number of days that may be granted to terminated employee to exercise awards prior to termination	15 days
Total unrecognized estimated unvested stock option compensation cost	$ 2,800,000
Weighted-average period of recognition of unrecognized compensation cost (years)	1 year 5 months
RSU grant date fair value			$ 23.96
Performance Shares [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
RSU grant date fair value	$ 191.76	$ 120.94	$ 78.71
Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock-based compensation expense	$ 77,400,000	$ 46,300,000	$ 22,900,000
Deferred Stock Units [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Restricted stock granted	13,632	18,018	38,400
RSU grant date fair value	$ 165.71	$ 123.38	$ 86.25
Stock-based compensation expense	$ 2,300,000	$ 2,600,000	$ 1,900,000
Minimum \| Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Restricted stock unit vesting period	3 years
Maximum \| Employee Stock Option
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration period of options from the date of grant	10 years
Expiration period for optionee who meets the 10% criteria	5 years
Maximum \| Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Restricted stock unit vesting period	4 years
ANSYS 1996 Employee Stock Purchase Plan [Member] \| Employee Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares authorized for grant under the plan	1,800,000.0
Expiration period of options from the date of grant	6 months
Share-based compensation arrangement by share-based payment award, maximum employee subscription rate	10.00%
Share-based compensation arrangement by share-based payment award, maximum number of shares per employee	3,840
Share-based compensation arrangement by share-based payment award, purchase price of common stock, percent	90.00%
Share-based compensation arrangement by share-based payment award, maximum dollar amount of common stock purchasable in a calendar year	$ 25,000
Share-based compensation arrangement by share-based payment award, shares issued in period	1,600,000
Stock-based compensation expense	$ 1,800,000	$ 1,200,000	$ 1,200,000
ANSYS 1996 Employee Stock Purchase Plan [Member] \| Maximum \| Employee Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, eligibility, ownership percentage	5.00%

Stock-Based Compensation (Stock-Based Compensation Expense) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 83,346	$ 53,154	$ 33,347
Related income tax benefits	(34,518)	(20,503)	(10,538)
Stock-based compensation expense, net of taxes	$ 48,828	$ 32,651	$ 22,809
Basic earnings per share	$ (0.58)	$ (0.38)	$ (0.26)
Diluted earnings per share	$ (0.57)	$ (0.38)	$ (0.26)
Software Licenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 0	$ 969	$ 701
Maintenance And Service
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	5,224	2,533	1,578
Selling, General And Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	47,099	30,817	15,990
Research And Development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 31,023	$ 18,835	$ 15,078

Stock-Based Compensation (Summary Of Stock Options) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning of year, Weighted-Average Exercise Price	$ 59.17	$ 56.37	$ 51.07
Granted, Weighted-Average Exercise Price	0.00	0.00	94.38
Exercised, Weighted-Average Exercise Price	50.92	49.78	45.57
Forfeited, Weighted-Average Exercise Price	86.28	80.92	72.07
Outstanding, end of year, Weighted-Average Exercise Price	62.80	59.17	56.37
Vested and Exercisable, end of year, Weighted-Average Exercise Price	59.69	55.11	51.80
Nonvested, Weighted-Average Exercise Price	$ 93.44	$ 91.71	$ 90.12
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning of year, Options	2,170	3,136	3,986
Granted, Options	0	0	260
Exercised, Options	(679)	(956)	(1,082)
Forfeited, Options	(7)	(10)	(28)
Outstanding, end of year, Options	1,484	2,170	3,136
Vested and Exercisable, end of year, Options	1,347	1,930	2,762
Nonvested, Options	137	240	374
Outstanding, Weighted-Average Remaining Contractual Term (in years)	3 years 6 months 18 days	4 years 1 month 6 days	4 years 7 months 14 days
Vested and Exercisable, Weighted-Average Remaining Contractual Term (in years)	3 years 1 month 22 days	3 years 6 months 26 days	4 years 15 days
Nonvested, Weighted-Average Remaining Contractual Term (in years)	7 years 7 months 5 days	8 years 3 months 20 days	8 years 11 months 6 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 78,648	$ 58,472	$ 49,752
Outstanding, Aggregate Intrinsic Value	118,908	191,895	113,822
Vested and Exercisable, Aggregate Intrinsic Value	112,133	178,456	112,379
Nonvested, Aggregate Intrinsic Value	6,775	13,439	1,443
Compensation Expense - Stock Options (in thousands)	$ 2,006	$ 2,948	$ 7,406

Stock-Based Compensation (Information Regarding Stock Options Outstanding) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2018 $ / shares shares
$5.91 - $48.97
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	$ 5.91
Range of Exercise Prices, Upper Limit	$ 48.97
Options Outstanding, Options \| shares	458
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	1 year 6 months 25 days
Options Outstanding, Weighted-Average Exercise Price	$ 42.12
Options Exercisable, Options \| shares	457
Options Exercisable, Weighted-Average Remaining Contractual Life (years)	1 year 6 months 22 days
Options Exercisable, Weighted-Average Exercise Price	$ 42.20
Options Unvested, Options \| shares	1
Options Unvested, Weighted-Average Remaining Contractual Life (years)	6 years
Options Unvested, Weighted-Average Exercise Price	$ 12.26
$58.67
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	58.67
Range of Exercise Prices, Upper Limit	$ 58.67
Options Outstanding, Options \| shares	359
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	2 years 10 months 4 days
Options Outstanding, Weighted-Average Exercise Price	$ 58.67
Options Exercisable, Options \| shares	359
Options Exercisable, Weighted-Average Remaining Contractual Life (years)	2 years 10 months 2 days
Options Exercisable, Weighted-Average Exercise Price	$ 58.67
Options Unvested, Options \| shares	0
Options Unvested, Weighted-Average Remaining Contractual Life (years)	0 years
Options Unvested, Weighted-Average Exercise Price	$ 0.00
$61.68 - $65.72
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	61.68
Range of Exercise Prices, Upper Limit	$ 65.72
Options Outstanding, Options \| shares	11
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	5 months 10 days
Options Outstanding, Weighted-Average Exercise Price	$ 63.75
Options Exercisable, Options \| shares	11
Options Exercisable, Weighted-Average Remaining Contractual Life (years)	5 months 10 days
Options Exercisable, Weighted-Average Exercise Price	$ 63.75
Options Unvested, Options \| shares	0
Options Unvested, Weighted-Average Remaining Contractual Life (years)	0 years
Options Unvested, Weighted-Average Exercise Price	$ 0.00
$67.44 - $95.09
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	67.44
Range of Exercise Prices, Upper Limit	$ 95.09
Options Outstanding, Options \| shares	656
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	5 years 4 months 18 days
Options Outstanding, Weighted-Average Exercise Price	$ 79.50
Options Exercisable, Options \| shares	520
Options Exercisable, Weighted-Average Remaining Contractual Life (years)	4 years 9 months 15 days
Options Exercisable, Weighted-Average Exercise Price	$ 75.68
Options Unvested, Options \| shares	136
Options Unvested, Weighted-Average Remaining Contractual Life (years)	7 years 7 months 9 days
Options Unvested, Weighted-Average Exercise Price	$ 94.16

Stock-Based Compensation (Assumptions To Estimate Fair Value Of Stock Awards) (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares	Dec. 31, 2017 $ / shares	Dec. 31, 2016 $ / shares
Employee Stock Option
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Risk-free interest rate, minimum	0.00%	0.00%	1.19%
Risk-free interest rate, maximum	0.00%	0.00%	1.93%
Expected dividend yield			0.00%
Expected volatility			24.00%
Expected term (in years)			5 years 8 months 17 days
Weighted-average fair value per share			$ 23.96
Restricted Stock Unit Compensation Expense [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Risk-free interest rate	2.40%	1.50%	1.00%
Expected dividend yield	0.00%	0.00%	0.00%
Expected term (in years)	2 years 9 months 18 days	2 years 9 months 18 days	2 years 9 months 18 days
Correlation factor	0.65	0.70	0.65
Weighted-average fair value per share	$ 191.76	$ 120.94	$ 78.71
Restricted Stock Unit Compensation Expense [Member] \| ANSYS Stock Price [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility	21.00%	19.00%	21.00%
Restricted Stock Unit Compensation Expense [Member] \| NASDAQ Composite Index [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility	15.00%	15.00%	16.00%

Stock-Based Compensation Stock-Based Compensation (Summary of Restricted Stock Units) (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested, beginning of year, RSUs	1,361	906	656
Granted, RSUs	681	866	588
Performance adjustment, RSUs	76	35	(90)
Vested, RSUs	(524)	(341)	(176)
Forfeited, RSUs	(72)	(105)	(72)
Nonvested, end of year, RSUs	1,522	1,361	906
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested, beginning of year, Weighted-Average Grant Date Fair Value, RSUs	$ 100.66	$ 86.45	$ 83.30
Granted, Weighted-Average Grant Date Fair Value, RSUs	163.67	109.67	87.50
Performance adjustment, Weighted-Average Grant Date Fair Value, RSUs	151.52	98.29	77.68
Vested, Weighted-Average Grant Date Fair Value, RSUs	101.38	88.58	83.79
Forfeited, Weighted-Average Grant Date Fair Value, RSUs	125.29	90.80	83.82
Nonvested, end of year, Weighted-Average Grant Date Fair Value, RSUs	$ 129.96	$ 100.66	$ 86.45

Stock-Based Compensation (Summary of Deferred Stock Awards to Non-Employee Directors) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Deferred awards outstanding, beginning of year	189,099
Shares diversified	0
Shares issued upon retirement	(56,400)
Deferred awards outstanding, end of year	132,699
Diversified Deferred Stock Award
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Deferred awards outstanding, beginning of year	29,500
Shares diversified	6,105
Shares issued upon retirement	(23,355)
Deferred awards outstanding, end of year	12,250
Undiversified Deferred Stock Award
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Deferred awards outstanding, beginning of year	159,599
Shares diversified	(6,105)
Shares issued upon retirement	(33,045)
Deferred awards outstanding, end of year	120,449

Stock Repurchase Program (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock Disclosures [Abstract]
Number of shares repurchased	1,674	2,750	3,700
Average price paid per share	$ 161.12	$ 122.20	$ 90.90
Total cost	$ 269,801	$ 336,042	$ 336,335

Stock Repurchase Program - Additional Information (Details) - shares	Dec. 31, 2018	Feb. 16, 2018
Class of Stock Disclosures [Abstract]
Stock repurchase program, number of shares authorized to be repurchased		5,000,000
Stock repurchase program, remaining number of shares authorized to be repurchased	3,800,000

Leases (Details) ft² in Thousands, $ in Thousands	12 Months Ended
Leases (Details) ft² in Thousands, $ in Thousands	Dec. 31, 2018 USD ($) ft²	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Operating Leased Assets [Line Items]
Lease rental expense incurred	$ 19,900	$ 17,100	$ 16,900
Future minimum lease payments	68,599
Future minimum lease payments, Year 1	16,354
Future minimum lease payments, Year 2	12,469
Future minimum lease payments, Year 3	10,177
Future minimum lease payments, Year 4	8,523
Future minimum lease payments, Year 5	6,809
Future minimum lease payments, Thereafter	$ 14,267
Lease Agreement Effective September 14, 2012 \| Canonsburg Office, New Company Headquarters
Operating Leased Assets [Line Items]
Area of real estate property \| ft²	186
Period of leased property	183 months
Base rent, years one through five	$ 4,300
Base rent, years six through ten	4,500
Base rent, years eleven through fifteen	4,700
Lease rental expense incurred	$ 4,400	$ 4,400	$ 4,400

Royalty Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
Royalty Agreements (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cost of goods and services sold	$ 155,885	$ 150,164	$ 146,860
Royalty
Cost of goods and services sold	$ 16,940	$ 15,963	$ 13,059

Revenue by Geographic Area (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 1,293,636	$ 1,095,250	$ 988,465
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	506,335	417,343	367,892
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	145,951	126,097	120,159
Germany
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	140,506	108,211	99,820
South Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	72,724	63,011	56,793
France
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	67,657	53,672	49,293
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	57,567	54,415	43,088
Other EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	193,317	166,472	151,250
Other international
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	109,579	$ 106,029	$ 100,170
Calculated under Revenue Guidance in Effect before Topic 606
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	1,216,469
Calculated under Revenue Guidance in Effect before Topic 606 \| United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	480,997
Calculated under Revenue Guidance in Effect before Topic 606 \| Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	137,733
Calculated under Revenue Guidance in Effect before Topic 606 \| Germany
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	124,729
Calculated under Revenue Guidance in Effect before Topic 606 \| South Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	62,215
Calculated under Revenue Guidance in Effect before Topic 606 \| France
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	62,146
Calculated under Revenue Guidance in Effect before Topic 606 \| China
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	56,060
Calculated under Revenue Guidance in Effect before Topic 606 \| Other EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	182,228
Calculated under Revenue Guidance in Effect before Topic 606 \| Other international
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 110,361

Property and Equipment by Geographic Area (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	$ 61,655	$ 57,096
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	46,605	45,498
India
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	4,176	3,704
EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	7,120	5,114
Other international
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	$ 3,754	$ 2,780

Unconditional Purchase Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unconditional Purchase Obligations (Excluding Capital Stock Redemptions) [Abstract]
Unconditional purchase obligations, beginning of year	$ 22,400	$ 14,100	$ 7,200
Future expenditures under purchase obligations, next twelve months	24,182
Future expenditures under purchase obligations, year two	8,588
Future expenditures under purchase obligations, year three	4,633
Future expenditures under purchase obligations, year four	54
Future expenditures under purchase obligations, year five	54
Future expenditures under purchase obligations	$ 37,511

Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended				15 Months Ended
Restructuring (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 331	$ 1,435	$ 6,176	$ 2,355	$ 10,297
Operating Income (Loss)
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 466	$ 2,000	$ 9,273	$ 3,419	$ 15,158

Contingencies and Commitments - Additional Information (Detail) $ in Millions	Dec. 31, 2018 USD ($)
India Service Tax Audit
Other Commitments And Contingencies [Line Items]
Loss contingency, estimate of possible loss	$ 7.1

Subsequent Events - Additional Information (Details) - Subsequent Event [Member] - USD ($) $ in Millions	Feb. 01, 2019	Feb. 22, 2019
Subsequent Event [Line Items]
Percentage of shares acquired	100.00%
Business combination, consideration transferred	$ 261.5
Line of credit facility, maximum borrowing capacity		$ 500.0

Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Provisions for doubtful accounts	$ 1,577	$ 1,474	$ 2,009
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	6,800	5,700	5,200
Provisions for doubtful accounts		1,474	2,009
Deductions - returns and write-offs	377	374	1,509
Balance at end of year	$ 8,000	$ 6,800	$ 5,700