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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2015	Feb. 16, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2015
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 Common Stock, Shares Outstanding		88,204,974
Entity Well-Known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 6,131,000,000

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 784,168	$ 788,064
Short-term investments	446	714
Accounts receivable, less allowance for doubtful accounts of $5,200 and $5,500, respectively	91,579	101,229
Other receivables and current assets	200,233	192,308
Total current assets	1,076,426	1,082,315
Property and equipment, net	61,924	64,643
Goodwill	1,332,348	1,312,182
Other intangible assets, net	220,553	259,312
Other long-term assets	5,757	6,187
Deferred income taxes	32,896	28,240
Total assets	2,729,904	2,752,879
Current liabilities:
Accounts payable	4,865	3,421
Accrued bonuses and commissions	46,141	47,001
Accrued income taxes	4,695	7,127
Other accrued expenses and liabilities	63,801	74,862
Deferred revenue	364,644	332,664
Total current liabilities	484,146	465,075
Long-term liabilities:
Deferred income taxes	2,091	16,190
Other long-term liabilities	49,240	54,113
Total long-term liabilities	51,331	70,303
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	894,469	904,825
Retained earnings	1,792,029	1,539,508
Treasury stock, at cost: 5,096,505 and 2,470,675 shares, respectively	(440,839)	(196,010)
Accumulated other comprehensive loss	(52,164)	(31,754)
Total stockholders’ equity	2,194,427	2,217,501
Total liabilities and stockholders’ equity	$ 2,729,904	$ 2,752,879

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue:
Software licenses	$ 555,105	$ 564,502	$ 528,944
Maintenance and service	387,648	371,519	332,316
Total revenue	942,753	936,021	861,260
Cost of sales:
Software licenses	29,105	30,607	28,363
Amortization	38,755	37,653	38,298
Maintenance and service	79,386	85,126	80,031
Total cost of sales	147,246	153,386	146,692
Gross profit	795,507	782,635	714,568
Operating expenses:
Selling, general and administrative	253,603	246,376	218,907
Research and development	168,831	165,421	151,439
Amortization	19,394	23,388	22,359
Total operating expenses	441,828	435,185	392,705
Operating income	353,679	347,450	321,863
Interest expense	(325)	(779)	(1,169)
Interest income	2,829	3,002	2,841
Other income (expense), net	582	(1,534)	(1,046)
Income before income tax provision	356,765	348,139	322,489
Income tax provision	104,244	93,449	77,162
Net income	$ 252,521	$ 254,690	$ 245,327
Earnings per share – basic:
Basic earnings per share (in USD per share)	$ 2.82	$ 2.77	$ 2.65
Weighted average shares - basic	89,561	92,067	92,691
Earnings per share – diluted:
Diluted earnings per share (in USD per share)	$ 2.76	$ 2.70	$ 2.58
Weighted average shares - diluted	91,502	94,194	95,139

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 5,200	$ 5,500
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	5,096,505	2,470,675
Commitments and contingencies

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 252,521	$ 254,690	$ 245,327
Other comprehensive loss:
Foreign currency translation adjustments	(20,410)	(29,110)	(11,295)
Comprehensive income	$ 232,111	$ 225,580	$ 234,032

- 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 252,521	$ 254,690	$ 245,327
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	77,670	81,924	80,701
Deferred income tax benefit	(15,196)	(18,859)	(24,025)
Provision for bad debts	1,304	2,104	1,465
Stock-based compensation expense	33,951	36,861	35,298
Excess tax benefits from stock-based compensation	(8,176)	(14,531)	(9,971)
Other	1,413	868	73
Changes in operating assets and liabilities:
Accounts receivable	6,044	(5,554)	(2,983)
Other receivables and current assets	(17,662)	(877)	(44,162)
Other long-term assets	273	(1,838)	(462)
Accounts payable, accrued expenses and current liabilities	(6,993)	8,208	15,737
Accrued income taxes	5,770	12,102	11,876
Deferred revenue	40,566	35,548	42,105
Other long-term liabilities	(3,962)	(5,339)	(17,996)
Net cash provided by operating activities	367,523	385,307	332,983
Cash flows from investing activities:
Acquisitions, net of cash acquired	(46,117)	(103,016)	(4,224)
Capital expenditures	(16,145)	(26,023)	(28,848)
Other investing activities	230	(231)	(105)
Net cash used in investing activities	(62,032)	(129,270)	(33,177)
Cash flows from financing activities:
Principal payments on long-term debt and capital leases	(21)	(91)	(53,149)
Purchase of treasury stock	(337,910)	(233,793)	(116,132)
Restricted stock withholding taxes paid in lieu of issued shares	(4,446)	(5,108)	(4,269)
Contingent consideration payments	(1,173)	(4,504)	(3,174)
Proceeds from shares issued for stock-based compensation	43,623	43,323	36,994
Excess tax benefits from stock-based compensation	8,176	14,531	9,971
Net cash used in financing activities	(291,751)	(185,642)	(129,759)
Effect of exchange rate fluctuations on cash and cash equivalents	(17,636)	(24,817)	(4,264)
Net (decrease) increase in cash and cash equivalents	(3,896)	45,578	165,783
Cash and cash equivalents, beginning of period	788,064	742,486	576,703
Cash and cash equivalents, end of period	784,168	788,064	742,486
Supplemental disclosures of cash flow information:
Income taxes paid	107,218	118,004	97,706
Interest paid	620	643	736
Fair value of stock options and restricted stock awards assumed in connection with acquisitions	3,528	68	0
Construction-in-progress - leased facility	$ 0	$ (18,136)	$ 18,136

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 Income (Loss)
Beginning balance at Dec. 31, 2012	$ 1,940,291	$ 932	$ 927,368	$ 1,039,491	$ (36,151)	$ 8,651
Beginning balance, shares at Dec. 31, 2012		93,202			536
Treasury shares acquired	$ (116,132)				$ (116,132)
Treasury shares acquired, shares	1,494				1,494
Stock-based compensation activity, including tax benefit	$ 78,055		(1,337)		$ 79,392
Stock-based compensation activity, including tax benefit, shares		(34)			(1,112)
Other comprehensive loss	(11,295)					(11,295)
Net income for the year	245,327			245,327
Ending balance at Dec. 31, 2013	2,136,246	$ 932	926,031	1,284,818	$ (72,891)	(2,644)
Ending balance, shares at Dec. 31, 2013		93,236			918
Treasury shares acquired	$ (233,793)				$ (233,793)
Treasury shares acquired, shares	2,977				2,977
Stock-based compensation activity, including tax benefit	$ 90,046		(20,628)		$ 110,674
Stock-based compensation activity, including tax benefit, shares					(1,424)
Other comprehensive loss	(29,110)					(29,110)
Net income for the year	254,690			254,690
Acquisition-related activity	(578)		(578)
Ending balance at Dec. 31, 2014	2,217,501	$ 932	904,825	1,539,508	$ (196,010)	(31,754)
Ending balance, shares at Dec. 31, 2014		93,236			2,471
Treasury shares acquired	$ (337,910)				$ (337,910)
Treasury shares acquired, shares	3,833				3,833
Stock-based compensation activity, including tax benefit	$ 79,197		(8,434)		$ 87,631
Stock-based compensation activity, including tax benefit, shares					(1,139)
Other comprehensive loss	(20,410)					(20,410)
Net income for the year	252,521			252,521
Acquisition-related activity	3,528		(1,922)		$ 5,450
Acquisition-related activity, shares					(68)
Ending balance at Dec. 31, 2015	$ 2,194,427	$ 932	$ 894,469	$ 1,792,029	$ (440,839)	$ (52,164)
Ending balance, shares at Dec. 31, 2015		93,236			5,097

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (PARENTHETICAL) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Stockholders' Equity [Abstract]
Stock-based compensation activity, tax benefit	$ 6,068	$ 14,970	$ 10,033

Organization	12 Months Ended
Organization	Dec. 31, 2015
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 technologies widely used by engineers, designers, researchers and students across a broad spectrum of industries and academia, including aerospace and defense, automotive, industrial equipment, electronics, biomedical, energy, materials and chemical processing, and semiconductors. As of January 1, 2015, the Company began to operate as one segment when two legal entities merged and a third insignificant acquired segment was no longer separately reported internally. 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, 2015

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.

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.

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


•	Uncertain tax positions


•	Tax valuation reserves


•	Fair value of stock-based compensation


•	Contract revenue


•	Useful lives for depreciation and amortization


•	Valuations of goodwill and other intangible assets


•	Contingent consideration


•	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 is derived principally from the licensing of computer software products and from related maintenance contracts. Revenue from perpetual licenses is classified as license revenue and is recognized upon delivery of the licensed product and the utility that enables the customer to access authorization keys, provided that acceptance has occurred and a signed contractual obligation has been received, the price is fixed and determinable, and collectibility of the receivable is probable. The Company determines the fair value of PCS sold together with perpetual licenses based on the rate charged for PCS when sold separately. Revenue from PCS contracts is classified as maintenance and service revenue and is recognized ratably over the term of the contract.

Revenue for software lease licenses is classified as license revenue and is 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, cannot be separated from lease revenue for accounting purposes. As a result, both the lease licenses and PCS are recognized ratably over the lease period. Due to the short-term nature of the software lease licenses and the frequency with which the Company provides major product upgrades (typically every 12–18 months), the Company does not believe that a significant portion of the fee paid under the arrangement is attributable to the PCS component of the arrangement and, as a result, includes the revenue for the entire arrangement within software license revenue in the consolidated statements of income.

Many of the Company's semiconductor products are typically licensed via longer term leases of 24–36 months. The Company recognizes revenue for these licenses over the term of the lease contract. Because the Company does not have vendor-specific objective evidence of the fair value of these leases, the Company also recognizes 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 is recognized as the services are performed. The Company applies the specific performance method to contracts in which the service consists of a single act, such as providing a training class to a customer, and the proportional performance method to other service contracts that are longer in duration and often include multiple acts (for example, both training and consulting). In applying the proportional performance method, 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 when the channel partner submits a written purchase commitment, collectibility from the channel partner is probable, a license agreement signed by the end-user customer is received and delivery has occurred, provided that all other revenue recognition criteria are satisfied. 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 based on the rate charged for PCS when sold separately, and 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 substantially perform as specified in the Company's most 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. Consequently, the Company has not established reserves for warranty obligations.

Cash and Cash Equivalents

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



	December 31, 2015			December 31, 2014
(in thousands, except percentages)	Amount		% of Total	Amount		% of Total
Cash accounts	$	427,244	54.5	$	506,731	64.3
Money market mutual funds	356,924		45.5	281,333		35.7
Total	$	784,168		$	788,064

The Company's money market mutual 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.

Software Development Costs

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, acquired software and technology, and a non-compete agreement. 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 $58.1 million, $61.0 million and $60.7 million for the years ended December 31, 2015, 2014 and 2013, 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. Goodwill is tested at the 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 on 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)	2015		2014		2013
Revenue from channel partners	24	%	25	%	25	%
Largest channel partner	5	%	4	%	6	%
2^nd largest channel partner	2	%	2	%	2	%

No single customer accounted for more than 5% of the Company's revenue in 2015, 2014 or 2013.

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)	2015		2014
Cash and cash equivalents held domestically	$	539,031	$	556,328
Cash and cash equivalents held by foreign subsidiaries	245,137		231,736
Cash and cash equivalents held in excess of deposit insurance, foreign and domestic	763,400		747,911
Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic	440,650		350,628

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 doubtful accounts of $1.3 million, $2.1 million and $1.5 million for the years ended December 31, 2015, 2014 and 2013, 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 their 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 accompanying 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 income (expense), net. The Company recorded net foreign exchange gains of $0.5 million for the year ended December 31, 2015 and net foreign exchange losses of $1.6 million and $1.1 million for the years ended December 31, 2014 and 2013, respectively.

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 options 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)	2015		2014		2013
Net income	$	252,521	$	254,690	$	245,327
Weighted average shares outstanding – basic	89,561		92,067		92,691
Dilutive effect of stock plans	1,941		2,127		2,448
Weighted average shares outstanding – diluted	91,502		94,194		95,139
Basic earnings per share	$	2.82	$	2.77	$	2.65
Diluted earnings per share	$	2.76	$	2.70	$	2.58
Anti-dilutive options	206		718		885

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, 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. The fair values of investments are based on quoted market prices for those or similar investments.

New Accounting Guidance

Balance sheet classification of deferred taxes: In November 2015, the FASB issued Accounting Standards Update No. 2015-17, Balance Sheet Classification of Deferred Taxes (ASU 2015-17). ASU 2015-17 requires all deferred tax assets and liabilities to be classified as long-term on the balance sheet. Prior guidance required both current and long-term classification, if applicable. The guidance was early adopted by the Company during the year ended December 31, 2015 and applied retrospectively. As a result of the retrospective adoption, the Company reclassified certain deferred taxes of $7.0 million to long-term deferred tax assets and $21.2 million to long-term deferred tax liabilities on the December 31, 2014 consolidated balance sheet.

Measurement-period adjustments related to business combinations: In September 2015, the FASB issued Accounting Standards Update No. 2015-16, Simplifying the Accounting for Measurement-Period Adjustments (ASU 2015-16). ASU 2015-16 requires adjustments to provisional amounts that are identified during the measurement period to be recognized in the period in which the adjustments are determined. The acquirer must record the effect on earnings of changes in depreciation, amortization or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date. Prior guidance required the restatement of prior periods if the adjustments impacted those periods. The guidance was early adopted by the Company during the quarter ended September 30, 2015 and applied prospectively. The impact on the Company's financial position, results of operations and cash flows was not material.

Revenue from contracts with customers: In May 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (ASU 2014-09). ASU 2014-09 supersedes most current revenue recognition guidance, including industry-specific guidance. Current guidance requires an entity to recognize revenue when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the seller's price to the buyer is fixed or determinable, and collectibility is reasonably assured. Under the new guidance, an entity is required 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. ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, delayed the effective date of ASU 2014-09 to annual periods beginning after December 15, 2017, including interim periods within that reporting period. Entities have the option of using a full retrospective, cumulative effect or modified approach to adopt ASU 2014-09. This update will impact the timing and amounts of revenue recognized. The Company is currently evaluating the effect that implementation of this update will have on its financial results upon adoption.

Acquisitions

12 Months Ended

Dec. 31, 2015

Business Combinations [Abstract]

Acquisitions

2015 Acquisitions

During the twelve months ended December 31, 2015, the Company completed various acquisitions to 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 price of the acquisitions was approximately $49.7 million, which included cash and equity.

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.

The total consideration transferred was allocated to the assets and liabilities of each acquisition based on management's estimates of the fair values of the assets acquired and liabilities assumed. The allocation included $24.5 million to identifiable intangible assets to be amortized over periods between five and ten years, and $27.5 million to goodwill, inclusive of any measurement-period adjustments recorded since the respective acquisition dates. The fair values of the assets acquired and liabilities assumed are based on provisional calculations and the estimates and assumptions for these items are subject to change during the measurement period (up to one year from the acquisition date) 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.

In valuing deferred revenue on the balance sheet as of each acquisition date, the Company applied the fair value provisions applicable to the accounting for business combinations. Acquired deferred revenues with a combined historical carrying value of $0.9 million were ascribed no fair value on the opening balance sheets. 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 each acquiree absent the acquisitions. The impact on reported revenue for the twelve months ended December 31, 2015 was $0.8 million. The expected impact on reported revenue is $0.1 million for the year ending December 31, 2016.

SpaceClaim Corporation

On April 30, 2014, the Company completed the acquisition of SpaceClaim, a leading provider of 3-D modeling technology. Under the terms of the agreement, ANSYS acquired SpaceClaim for a purchase price of $85.0 million, which was paid almost entirely in cash.

SpaceClaim's software provides customers with a powerful and intuitive 3-D direct modeling solution to author new concepts and then leverage the power of simulation to rapidly iterate on these designs to drive innovation. The broad appeal of the SpaceClaim technology can help the Company deliver simulation tools to any engineer in any industry. The complementary combination is expected to accelerate the development of new and innovative products to the marketplace while lowering design and engineering costs for customers.

The operating results of SpaceClaim have been included in the Company's consolidated financial statements from April 30, 2014, the date of acquisition.

The assets and liabilities of SpaceClaim 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, as adjusted within the one-year measurement period:

Fair Value of Consideration Transferred:



(in thousands)
Cash	$	84,892
ANSYS replacement stock options	68
Total consideration transferred at fair value	$	84,960

Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed:



(in thousands)
Cash	$	723
Accounts receivable and other tangible assets	1,857
Developed technology (10-year life)	15,800
Customer relationships (6-year life)	9,400
Trade name (6-year life)	1,300
Contract backlog (6-year life)	550
Non-compete agreement (2-year life)	300
Net deferred tax assets	9,288
Accounts payable and other liabilities	(2,011		)
Deferred revenue	(700		)
Total identifiable net assets	$	36,507
Goodwill	$	48,453

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 SpaceClaim.

During the one-year measurement period since the SpaceClaim acquisition date, the Company adjusted the fair values of the assets acquired and liabilities assumed, with the offset recorded as a $4.8 million decrease to goodwill. These adjustments were made 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.

In valuing deferred revenue on the SpaceClaim 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 $3.3 million was ascribed a fair value of $0.7 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 SpaceClaim absent the acquisition. The impacts on reported revenue for the twelve months ended December 31, 2015 and 2014 were $0.6 million and $2.0 million, respectively.

Reaction Design

On January 3, 2014, the Company completed the acquisition of Reaction Design, a leading developer of chemistry simulation software. Under the terms of the agreement, ANSYS acquired Reaction Design for a purchase price of $19.1 million in cash. Reaction Design's solutions enable transportation manufacturers and energy companies to rapidly achieve their clean technology goals by automating the analysis of chemical processes via computer simulation and modeling solutions.

The operating results of Reaction Design have been included in the Company's consolidated financial statements since the date of acquisition, January 3, 2014. The total consideration transferred was allocated to the assets and liabilities of Reaction Design based on management's estimates of the fair values of the assets acquired and the liabilities assumed. The allocation included $7.0 million to identifiable intangible assets, including core technology, customer lists and trade names, to be amortized over periods between two and eleven years, and $9.2 million to goodwill, which is not tax-deductible. These amounts include measurement-period adjustments. During the one-year measurement period since the Reaction Design acquisition date, the Company adjusted the fair values of the assets acquired and liabilities assumed, with the offset recorded as an increase to goodwill of $1.9 million and a reduction in noncontrolling interest of $0.6 million. These adjustments were made 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.

In valuing deferred revenue on the Reaction Design 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 $2.3 million was ascribed no fair value 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 Reaction Design absent the acquisition. The impacts on reported revenue for the twelve months ended December 31, 2015 and 2014 were $0.3 million and $2.0 million, respectively.

EVEN - Evolutionary Engineering AG

On April 2, 2013, the Company acquired EVEN, a leading provider of composite analysis and optimization technology. Under the terms of the agreement, ANSYS acquired EVEN for a purchase price of $8.1 million, which consisted of $4.5 million in cash and an estimated $3.6 million of contingent consideration based on EVEN's achievement of certain technical milestones during the three years following the acquisition date. To date, the Company has paid $3.0 million, including imputed interest, of its contingent consideration related to the EVEN acquisition.

The total consideration transferred was allocated to the assets and liabilities of EVEN based on management's estimates of the fair values of the assets acquired and the liabilities assumed. The allocation included $2.6 million to identifiable intangible assets, including customer lists and core technology, to be amortized over a period of five years, and $5.9 million to goodwill, which is not tax-deductible.

- Definition

The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1497-128463

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1490-128463

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1392-128463

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
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-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e7008-128479

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1486-128463

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=56956791&loc=d3e4845-128472

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1500-128463

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1524-128463

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e7000-128479

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
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-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=56956791&loc=d3e4922-128472

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=56956791&loc=d3e4934-128472

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=56956791&loc=d3e4926-128472

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1383-128463

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
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-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6996-128479

+ Details

Other Receivables and Current Assets

12 Months Ended

Dec. 31, 2015

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Other Receivables and Current Assets

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



(in thousands)	December 31, 2015		December 31, 2014
Receivables related to unrecognized revenue	$	170,186	$	152,830
Income taxes receivable, including overpayments and refunds	7,877		18,276
Prepaid expenses and other current assets	22,170		21,202
Total other receivables and current assets	$	200,233	$	192,308

Receivables for unrecognized revenue represent the current portion of billings made for annual lease licenses and software maintenance that have not yet been recognized as revenue.

Property and Equipment

12 Months Ended

Dec. 31, 2015

Property, Plant and Equipment [Abstract]

Property and Equipment

Property and equipment consists of the following:



		December 31,
(in thousands)	Estimated Useful Lives	2015			2014
Equipment	1-10 years	$	78,932		$	75,500
Computer software	1-5 years	33,710			30,007
Buildings	10-40 years	25,041			24,526
Leasehold improvements	1-15 years	12,621			10,368
Furniture	1-13 years	8,601			8,475
Land		1,759			2,140
Property and equipment, gross		160,664			151,016
Less: Accumulated depreciation		(98,740		)	(86,373		)
Property and equipment, net		$	61,924		$	64,643

Depreciation expense related to property and equipment, including the amounts acquired through capital lease commitments, was $19.5 million, $20.9 million and $19.9 million for the years ended December 31, 2015, 2014 and 2013, respectively.

Goodwill and Intangible Assets

12 Months Ended

Dec. 31, 2015

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 2015, the Company completed the annual impairment test for goodwill and indefinite-lived intangible assets and determined that these assets had not been impaired as of the test date, January 1, 2015. The Company tested a previously unamortized trade name that was determined to have a finite life for impairment during the first quarter of 2015 and determined that its fair value exceeded its carrying value, so no impairment was recorded. No other events occurred or circumstances changed during the year ended December 31, 2015 that would indicate that the fair values of the Company's reporting units and indefinite-lived intangible assets are below their carrying amounts.

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



	December 31, 2015					December 31, 2014
(in thousands)	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
Finite-lived intangible assets:
Developed software and core technologies (3 – 11 years)	$	336,262	$	(251,201	)	$	321,076	$	(227,298	)
Customer lists and contract backlog (5 – 15 years)	159,885		(76,160		)	221,159		(121,380		)
Trade names (2 – 10 years)	127,903		(76,493		)	114,432		(63,082		)
Non-compete agreement	—		—			300		(52		)
Total	$	624,050	$	(403,854	)	$	656,967	$	(411,812	)
Indefinite-lived intangible assets:
Trade names	$	357				$	14,157

The decrease in unamortized trade names in the table above was due to the determination that a trade name no longer had an indefinite life. Amortization expense for the intangible assets reflected above was $58.1 million, $61.0 million and $60.7 million for the years ended December 31, 2015, 2014 and 2013, respectively.

As of December 31, 2015, estimated future amortization expense for the intangible assets reflected above is as follows:



(in thousands)
2016	$	50,574
2017	47,714
2018	34,368
2019	20,887
2020	19,787
Thereafter	46,866
Total intangible assets subject to amortization	220,196
Indefinite-lived trade name	357
Other intangible assets, net	$	220,553

The changes in goodwill during the years ended December 31, 2015 and 2014 are as follows:



(in thousands)	2015			2014
Beginning balance - January 1	$	1,312,182		$	1,255,704
Acquisitions	28,561			60,484
Adjustments⁽¹⁾	(4,573		)	619
Currency translation	(3,822		)	(4,625		)
Ending balance - December 31	$	1,332,348		$	1,312,182

⁽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.

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Long-Term Debt

12 Months Ended

Dec. 31, 2015

Debt Disclosure [Abstract]

Long-Term Debt

The Company paid the outstanding balance on its term loan at maturity on July 31, 2013. For the year ended December 31, 2013, the Company recorded interest expense related to the term loan at an average interest rate of 1.04%. The interest expense on the term loan and amortization related to debt financing costs were as follows:



	Year Ended December 31, 2013
(in thousands)	Interest Expense		Amortization
July 31, 2008 term loan	$	230	$	149

Fair Value Measurement

12 Months Ended

Dec. 31, 2015

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 and liabilities carried at fair value and measured on a recurring basis:



				Fair Value Measurements at Reporting Date Using:
(in thousands)	December 31, 2015			Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents	$	356,924		$	356,924	$	—	$	—
Short-term investments	$	446		$	—	$	446	$	—
Liabilities
Contingent consideration	$	(1,376	)	$	—	$	—	$	(1,376	)



				Fair Value Measurements at Reporting Date Using:
(in thousands)	December 31, 2014			Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents	$	281,333		$	281,333	$	—	$	—
Short-term investments	$	714		$	—	$	714	$	—
Liabilities
Contingent consideration	$	(2,621	)	$	—	$	—	$	(2,621	)

The cash equivalents in the preceding tables represent money market mutual funds.

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 contingent consideration in the preceding tables represents potential future payments related to the EVEN acquisition in accordance with the 2013 merger agreement. The net present value calculations for the contingent consideration include significant unobservable inputs in the assumption that all remaining payments will be made, and, therefore, the liabilities were classified as Level 3 in the fair value hierarchy.

The following table presents the changes during the years ended December 31, 2015 and 2014 in the Company's Level 3 liabilities for contingent consideration and deferred compensation that are measured at fair value on a recurring basis:



	Fair Value Measurement Using Significant Unobservable Inputs
(in thousands)	Contingent Consideration			Deferred Compensation
Balance as of January 1, 2014	$	7,389		$	704
Contingent payments	(4,866		)	(712		)
Interest expense and foreign exchange activity included in earnings	98			8
Balance as of December 31, 2014	$	2,621		$	—
Contingent payments	(1,456		)	—
Interest expense and foreign exchange activity included in earnings	211			—
Balance as of December 31, 2015	$	1,376		$	—

The carrying values of cash, accounts receivable, accounts payable, accrued expenses, other accrued liabilities and short-term obligations approximate their fair values because of their short-term nature.

Income Taxes

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Income Taxes

Income before income taxes includes the following components:



	Year Ended December 31,
(in thousands)	2015		2014		2013
Domestic	$	325,097	$	291,042	$	272,569
Foreign	31,668		57,097		49,920
Total	$	356,765	$	348,139	$	322,489

The provision for income taxes is composed of the following:



	Year Ended December 31,
(in thousands)	2015			2014			2013
Current:
Federal	$	93,853		$	80,620		$	69,268
State	7,733			7,192			7,197
Foreign	17,854			24,495			24,722
Deferred:
Federal	(14,472		)	(18,536		)	(23,438		)
State	(1,987		)	(1,915		)	(2,187		)
Foreign	1,263			1,593			1,600
Total	$	104,244		$	93,449		$	77,162

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



	Year Ended December 31,
	2015		2014		2013
Federal statutory tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal benefit	1.1		1.2		1.1
Stock-based compensation	—		0.6		0.9
Net benefit of unrepatriated earnings	—		(0.3	)	(0.9	)
Uncertain tax positions	(0.4	)	(0.9	)	(3.7	)
Research and development credits	(1.1	)	(1.1	)	(2.0	)
Benefit from restructuring activities	(2.7	)	(4.1	)	(2.8	)
Domestic production activity benefit	(3.1	)	(3.5	)	(3.3	)
Other	0.4		(0.1	)	(0.4	)
	29.2	%	26.8	%	23.9	%

In general, it is the practice and intention of the Company to repatriate previously taxed earnings and to reinvest all other earnings of its non-U.S. subsidiaries. The Company has not made a provision for U.S. taxes on $202.9 million, representing the excess of the amount for financial reporting over the tax bases of investments in foreign subsidiaries that are essentially permanent in duration. Generally, such amounts become subject to U.S. taxation upon the remittance of dividends and under certain other circumstances. The residual U.S. tax cost associated with this difference is estimated to be $20.9 million.

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



	December 31,
(in thousands)	2015			2014
Deferred tax assets:
Net operating loss carryforwards	$	40,939		$	42,060
Stock-based compensation	23,258			23,331
Employee benefits	17,044			20,034
Uncertain tax positions	10,233			8,545
Deferred revenue	8,603			6,533
Research and development credits	3,562			4,349
Allowance for doubtful accounts	1,888			1,806
Other	3,240			2,877
Valuation allowance	(603		)	(130		)
	108,164			109,405
Deferred tax liabilities:
Other intangible assets	(73,933		)	(92,703		)
Property and equipment	(3,426		)	(4,652		)
	(77,359		)	(97,355		)
Net deferred tax assets	$	30,805		$	12,050

The Company excluded from the above table a $9.3 million deferred tax asset associated with foreign net operating loss carryforwards and a corresponding $9.3 million valuation allowance generated during the current year in a jurisdiction where the Company determined utilization is remote. The net increase in the gross valuation allowance was $0.7 million. This increase was primarily due to acquired state losses that are not expected to be utilized.

As of December 31, 2015, the Company had federal net operating loss carryforwards of $40.8 million. These losses expire between 2020 - 2034, and are subject to limitations on their utilization. Deferred tax assets of $1.6 million have been recorded for state operating loss carryforwards. These losses expire between 2016 - 2035, and are subject to limitations on their utilization. The Company had total foreign net operating loss carryforwards of $84.0 million, of which $29.4 million are not currently subject to expiration dates. The remainder, $54.6 million, expires between 2019 - 2025. The Company had tax credit carryforwards of $4.7 million, of which $3.0 million are subject to limitations on their utilization. Approximately $0.7 million of these tax credit carryforwards are not currently subject to expiration dates. The remainder, $4.0 million, expires in various years between 2016 - 2035.

In December 2013, the Company received notice from the Internal Revenue Service that the Joint Committee on Taxation took no exception to the Company's tax returns that were filed for 2009 and 2010. An $11.0 million tax benefit was recognized in the Company's 2013 financial results as the Company had effectively settled uncertainty regarding refund claims filed in connection with those returns.

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



	Year Ended December 31,
(in thousands)	2015			2014			2013
Unrecognized tax benefit as of January 1	$	16,342		$	19,590		$	37,203
Gross increases—tax positions in prior period	64			488			320
Gross decreases—tax positions in prior period	(850		)	(3,715		)	(18,058		)
Gross increases—tax positions in current period	4,064			2,513			2,036
Reductions due to a lapse of the applicable statute of limitations	(2,808		)	(1,924		)	(1,734		)
Changes due to currency fluctuation	(653		)	(610		)	20
Settlements	(92		)	—			(197		)
Unrecognized tax benefit as of December 31	$	16,067		$	16,342		$	19,590

The Company believes that it is reasonably possible that approximately $0.4 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, 2015, $10.5 million would affect the effective tax rate, if recognized.

The Company recognizes interest and penalties related to income taxes as income tax expense. As of December 31, 2015, the Company accrued a liability for penalties of $1.9 million and interest of $2.7 million. As of December 31, 2014, the Company accrued a liability for penalties of $1.6 million and interest of $2.7 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 2013, 2014 and 2015 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, 2015
Compensation and Retirement Disclosure [Abstract]
Pension And Profit-Sharing Plans	Pension and Profit-Sharing Plans The Company has a 401(k)/profit-sharing plan for all qualifying salaried domestic employees that permits participants to make contributions by salary reduction 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 funds the foreign defined benefit and contribution plans based on the minimum required deposits according to the local statutory requirements. The unfunded portion of the defined benefit obligation for each plan is accrued in other long-term liabilities. Expenses related to the Company's retirement programs were $8.4 million in 2015, $8.9 million in 2014 and $8.0 million in 2013.

Non-Compete and Employment Agreements	12 Months Ended
Non-Compete and Employment Agreements	Dec. 31, 2015
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), 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 the Chief Executive Officer. This agreement provides for, among other things, minimum severance payments equal to his base salary, target bonus and then-existing benefits through the earlier of the second anniversary of the termination date if the Chief Executive Officer is terminated without cause or when he accepts other employment. The Chief Executive Officer is subject to a two-year restriction on competition following termination of employment under the circumstances described in the contract. 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, 2015

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

Stock-Based Compensation

The Company has a stock option and grant plan—the Fourth Amended and Restated 1996 Stock Option and Grant Plan ("Stock Plan"). The Stock Plan, as amended, authorizes the grant of up to 30,400,000 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) stock appreciation rights and (ix) 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.

In the event of a "sale event" as defined in the Stock Plan, 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, 2015, 2014 and 2013 is as follows:



	Year Ended December 31,
(in thousands, except per share amounts)	2015			2014			2013
Cost of sales:
Software licenses	$	745		$	1,776		$	1,349
Maintenance and service	1,868			2,035			2,293
Operating expenses:
Selling, general and administrative	17,153			17,073			16,847
Research and development	14,185			15,977			14,809
Stock-based compensation expense before taxes	33,951			36,861			35,298
Related income tax benefits	(11,656		)	(10,927		)	(11,096		)
Stock-based compensation expense, net of taxes	$	22,295		$	25,934		$	24,202
Net impact on earnings per share:
Basic earnings per share	$	(0.25	)	$	(0.28	)	$	(0.26	)
Diluted earnings per share	$	(0.24	)	$	(0.28	)	$	(0.25	)

Information regarding stock option transactions is summarized below:



	Year Ended December 31,
	2015				2014				2013
(options in thousands)	Options		Weighted- Average Exercise Price		Options		Weighted- Average Exercise Price		Options		Weighted- Average Exercise Price
Outstanding, beginning of year	4,932		$	48.76	6,166		$	44.77	7,122		$	42.85
Granted	57		$	88.10	150		$	81.09	103		$	81.87
Issued pursuant to acquisitions	8		$	12.26	21		$	23.26	—		$	—
Exercised	(975	)	$	40.52	(1,266	)	$	31.36	(993	)	$	34.26
Forfeited	(36	)	$	70.15	(139	)	$	61.11	(66	)	$	53.75
Outstanding, end of year	3,986		$	51.07	4,932		$	48.76	6,166		$	44.77
Vested and Exercisable, end of year	3,539		$	48.29	3,958		$	44.22	4,351		$	38.18



	2015		2014		2013
Weighted-Average Remaining Contractual Term (in years)
Outstanding	4.85		5.53		5.99
Vested and Exercisable	4.53		5.00		5.13
Aggregate Intrinsic Value (in thousands)
Outstanding	$	165,131	$	163,932	$	261,601
Vested and Exercisable	$	156,487	$	149,536	$	213,304

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 for 2015, 2014 and 2013.

The table below presents the weighted average input assumptions used and resulting fair values for options granted or issued in business combinations during each respective year:



	Year Ended December 31,
	2015	2014	2013
Risk-free interest rate	1.18% to 1.65%	1.49% to 1.76%	0.68% to 1.48%
Expected dividend yield	—%	—%	—%
Expected volatility	25%	35%	37%
Expected term	5.6 years	5.7 years	5.8 years
Weighted-average fair value per share	$30.83	$32.26	$29.85

As stock-based compensation expense recognized in the consolidated statements of income is based on awards ultimately expected to vest, it must be reduced for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. 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. The total estimated grant-date fair values of stock options that vested during the years ended December 31, 2015, 2014 and 2013 were $12.3 million, $19.5 million and $24.7 million, respectively. As of December 31, 2015, total unrecognized estimated compensation cost related to unvested stock options granted prior to that date was $10.1 million, which is expected to be recognized over a weighted-average period of 1.4 years. The total intrinsic values of stock options exercised during the years ended December 31, 2015, 2014 and 2013 were $47.1 million, $60.6 million and $45.2 million, respectively. As of December 31, 2015, 0.4 million unvested options with an aggregate intrinsic value of $9.2 million are expected to vest and have a weighted-average exercise price of $73.13 and a weighted-average remaining contractual term of 7.4 years. The Company recorded cash received from the exercise of stock options of $39.5 million and tax benefits related to all stock activity of $17.7 million for the year ended December 31, 2015.

Information regarding stock options outstanding as of December 31, 2015 is summarized below:



(options in thousands)	Options Outstanding				Options Exercisable
Range of Exercise Prices	Options	Weighted- Average Remaining Contractual Life (years)	Weighted- Average Exercise Price		Options	Weighted- Average Exercise Price
$5.91 - $38.75	1,030	2.49	$	29.68	1,019	$	29.81
$38.86 - $48.97	1,077	4.27	$	45.39	1,077	$	45.39
$51.52 - $65.72	802	5.64	$	58.68	794	$	58.64
$67.34 - $94.15	1,077	7.08	$	71.55	649	$	69.43

Under the terms of the ANSYS, Inc. Long-Term Incentive Plan, the Company issues various restricted stock awards, which may have a market condition, an operating performance condition or a service condition, or any combination of the three. The Company granted 34,450, 47,000 and 94,300 performance-based restricted stock units with a market condition in 2015, 2014 and 2013, respectively. The percentage of the award that vests is based on the Company's performance as measured by total shareholder return relative to the median percentage appreciation of a specified stock index over the measurement period, subject to each participant's continued employment with the Company through the conclusion of the measurement period. The measurement periods for the restricted stock units granted pursuant to the Long-Term Incentive Plan are one-, two- and three-year periods beginning January 1 of the year of the grant. Each restricted stock unit relates to one share of the Company's common stock. The weighted-average fair value of each restricted stock unit granted in 2015, 2014 and 2013 was estimated on the grant date to be $81.61, $65.94 and $50.05, respectively. The fair value of the restricted stock units was estimated using a Monte Carlo simulation model. The determination of the fair value of the awards was affected by the grant date and a number of variables, each of which has been identified in the chart below. Share-based compensation expense based on the fair value of the award is being recorded from the grant date through the conclusion of the three-year measurement period. Total compensation expense associated with the market condition awards recorded for the years ended December 31, 2015, 2014 and 2013 was $3.1 million, $2.5 million and $3.6 million, respectively.



	Year Ended December 31,
Assumptions used in Monte Carlo lattice pricing model	2015	2014	2013
Risk-free interest rate	1.1%	0.7%	0.4%
Expected dividend yield	—%	—%	—%
Expected volatility—ANSYS stock price	23%	25%	25%
Expected volatility—NASDAQ Composite Index	14%	15%	20%
Expected term	2.8 years	2.8 years	2.8 years
Correlation factor	0.60	0.70	0.70

During 2015, the Company issued 51,795 restricted stock awards with vesting conditions based on defined operating metrics and a weighted-average grant-date fair value of $86.38. During 2014, the Company issued 20,667 restricted stock awards with vesting conditions based on defined operating metrics and a weighted-average grant-date fair value of $81.52. The grant-date fair value of the awards is being recorded from the grant date through the conclusion of the measurement period associated with each operating metric based on management's estimates concerning the probability of vesting. Total compensation expense associated with these awards recorded for the years ended December 31, 2015 and 2014 was $0.4 million and $0.1 million, respectively.

In addition, in 2015 and 2014, the Company granted restricted stock units of 344,500 and 364,150, respectively, that will vest over a four-year period with a weighted-average grant-date fair value of $86.34 and $82.13, respectively. During 2015, 85,713 shares vested and were released. As of December 31, 2015 and 2014, 571,462 and 344,750 units were outstanding, respectively. Total compensation expense is being recorded over the four-year service period and was $12.5 million and $5.8 million for the years ended December 31, 2015 and 2014, respectively.

In conjunction with a 2015 acquisition, ANSYS issued 68,451 shares of replacement restricted stock with a weighted-average grant-date fair value of $90.48. Of the $6.2 million grant-date fair value, $3.5 million, related to partially vested awards, was recorded as non-cash purchase price consideration. The remaining fair value will be recognized as stock compensation expense through the conclusion of the service period. During the year ended December 31, 2015, the Company recorded $0.6 million of stock compensation expense related to these awards.

In conjunction with a 2011 acquisition, the Company granted performance-based restricted stock awards. Vesting was determined based on the achievements of certain revenue and operating income targets of the entity post-acquisition. Total compensation expense associated with the awards recorded for the years ended December 31, 2014 and 2013 was $4.7 million and $3.8 million, respectively.

The Company has granted deferred stock units to non-affiliate Independent Directors, which are rights to receive shares of common stock upon termination of service as a Director. The deferred stock units were issued quarterly in arrears and vested immediately upon grant. As of December 31, 2015, 189,099 deferred stock units have been earned with the underlying shares remaining unissued until the service termination of the respective Director owners. Of this amount, 43,134 units were earned during the year ended December 31, 2015. Total compensation expense associated with the awards recorded for the years ended December 31, 2015, 2014 and 2013, was $4.0 million, $3.5 million and $2.5 million, respectively.

Stock Repurchase Program

12 Months Ended

Dec. 31, 2015

Equity [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)	2015		2014		2013
Number of shares repurchased	3,833		2,977		1,494
Average price paid per share	$	88.16	$	78.54	$	77.73
Total cost	$	337,910	$	233,793	$	116,132

In February 2016, the Company's Board of Directors increased the number of shares authorized for repurchase to a total of 5.0 million shares under the stock repurchase program. As of December 31, 2015, 2.1 million shares remained available for repurchase under the program.

Employee Stock Purchase Plan	12 Months Ended
Employee Stock Purchase Plan	Dec. 31, 2015
Equity [Abstract]
Employee Stock Purchase Plan	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 on May 6, 2004 to increase the number of shares available for offerings to 1.6 million shares. The Purchase Plan was amended and restated in 2007. 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. As of December 31, 2015, 1.4 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, 2015, 2014 and 2013 was $1.0 million, $0.9 million and $0.8 million, respectively.

Leases

12 Months Ended

Dec. 31, 2015

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 lease was effective as of September 14, 2012, but because the leased premises were under construction, the Company was not obligated to pay rent until three months following the date that the leased premises were delivered to ANSYS, which occurred on October 1, 2014. The term of the lease is 183 months, beginning on October 1, 2014. 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 and $0.8 million in lease expense related to this facility during the years ended December 31, 2015 and 2014, respectively.

The Company's corporate headquarters was previously located in a separate office facility, also in Canonsburg, Pennsylvania. The Company occupied this space until November 2014, and the lease term expired on December 31, 2014. Lease expense related to this facility was $1.4 million in each of the years ended December 31, 2014 and 2013.

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

Office space lease expense totaled $16.5 million, $15.8 million and $14.1 million for the years ended December 31, 2015, 2014 and 2013, respectively. Future minimum lease payments, including termination fees, under noncancellable operating leases for office space in effect at December 31, 2015 are as follows:



(in thousands)	Total		2016		2017		2018		2019		2020		Thereafter
Future minimum lease payments	$	71,887	$	13,800	$	10,449	$	7,834	$	7,043	$	6,195	$	26,566

Sale-Leaseback Arrangement

The lease agreement terms for the new Canonsburg headquarters facility provide that the Company was responsible for paying the cost of certain tenant improvements that exceeded an allowance to be paid by the landlord. There was no cap to the Company's obligation in excess of the landlord allowance. As a result, the Company was considered the owner of the building during the construction period and the lease was subject to sale-leaseback treatment.

The building was completed and delivered to the Company on October 1, 2014. The Company determined that the lease does not meet the criteria for capital lease treatment under the accounting guidance, and the Company does not have continuing involvement in the lease. As a result, the construction-in-progress asset and liability were removed from the consolidated balance sheets. The sale-leaseback treatment of the lease during the construction period did not have any impact on the Company's results of operations or cash flows.

Royalty Agreements	12 Months Ended
Royalty Agreements	Dec. 31, 2015
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 or revenue. Royalty fees are reported in cost of goods sold and were $11.8 million, $11.5 million and $10.3 million for the years ended December 31, 2015, 2014 and 2013, respectively.

Geographic Information (Notes)

12 Months Ended

Dec. 31, 2015

Segment Reporting [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)	2015		2014		2013
United States	$	354,433	$	320,327	$	292,323
Japan	104,299		108,757		108,064
Germany	94,546		99,714		93,525
South Korea	55,142		55,606		43,585
France	49,444		58,785		56,310
Canada	13,314		14,034		14,163
Other European	145,985		159,011		145,304
Other international	125,590		119,787		107,986
Total revenue	$	942,753	$	936,021	$	861,260

Property and equipment by geographic area is as follows:



	December 31,
(in thousands)	2015		2014
United States	$	47,971	$	49,957
Europe	6,808		7,840
India	3,286		3,123
Other international	3,859		3,723
Total property and equipment	$	61,924	$	64,643

Unconditional Purchase Obligations	12 Months Ended
Unconditional Purchase Obligations	Dec. 31, 2015
Unconditional Purchase Obligations (Excluding Capital Stock Redemptions) [Abstract]
Unconditional Purchase Obligations	Unconditional Purchase Obligations The Company has entered into various unconditional purchase obligations which primarily include software licenses and long-term purchase contracts for network, communication and office maintenance services. The Company expended $5.3 million, $2.9 million and $3.3 million related to unconditional purchase obligations that existed as of the beginning of each year for the years ended December 31, 2015, 2014 and 2013, respectively. Future expenditures under unconditional purchase obligations in effect as of December 31, 2015 are $7.2 million in 2016, $1.3 million in 2017 and $0.7 million in 2018.

Contingencies and Commitments (Notes)	12 Months Ended
Contingencies and Commitments (Notes)	Dec. 31, 2015
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 received a formal inquiry after a service tax audit was held in 2011. The Company could incur tax charges and related liabilities, including those related to the service tax audit case, of approximately $6 million. The service tax issues raised in the Company's notice 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) has passed a ruling favorable 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 audit case. The Company is uncertain as to when the service tax audit will be completed. 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, 2015. 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.

Schedule II - Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2015

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, 2015 Allowance for doubtful accounts	$	5,500	$	1,304	$	1,604	$	5,200
Year ended December 31, 2014 Allowance for doubtful accounts	$	5,700	$	2,104	$	2,304	$	5,500
Year ended December 31, 2013 Allowance for doubtful accounts	$	4,800	$	1,465	$	565	$	5,700

Summary Of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Accounting Principles

The financial statements and accompanying notes are prepared in accordance with accounting principles generally accepted in the United States.

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.

Use Of Estimates


•	Allowances for doubtful accounts receivable


•	Income tax accruals


•	Uncertain tax positions


•	Tax valuation reserves


•	Fair value of stock-based compensation


•	Contract revenue


•	Useful lives for depreciation and amortization


•	Valuations of goodwill and other intangible assets


•	Contingent consideration


•	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

Cash And Cash Equivalents



	December 31, 2015			December 31, 2014
(in thousands, except percentages)	Amount		% of Total	Amount		% of Total
Cash accounts	$	427,244	54.5	$	506,731	64.3
Money market mutual funds	356,924		45.5	281,333		35.7
Total	$	784,168		$	788,064

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

Property And Equipment

Research And Development

Research and development costs, other than certain capitalized software development costs, are expensed as incurred.

Software Development Costs

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

Goodwill And Other Intangible Assets

Concentrations Of Credit Risk



	Year Ended December 31,
(as a % of revenue)	2015		2014		2013
Revenue from channel partners	24	%	25	%	25	%
Largest channel partner	5	%	4	%	6	%
2^nd largest channel partner	2	%	2	%	2	%

No single customer accounted for more than 5% of the Company's revenue in 2015, 2014 or 2013.



	As of December 31,
(in thousands)	2015		2014
Cash and cash equivalents held domestically	$	539,031	$	556,328
Cash and cash equivalents held by foreign subsidiaries	245,137		231,736
Cash and cash equivalents held in excess of deposit insurance, foreign and domestic	763,400		747,911
Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic	440,650		350,628

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



	Year Ended December 31,
(in thousands, except per share data)	2015		2014		2013
Net income	$	252,521	$	254,690	$	245,327
Weighted average shares outstanding – basic	89,561		92,067		92,691
Dilutive effect of stock plans	1,941		2,127		2,448
Weighted average shares outstanding – diluted	91,502		94,194		95,139
Basic earnings per share	$	2.82	$	2.77	$	2.65
Diluted earnings per share	$	2.76	$	2.70	$	2.58
Anti-dilutive options	206		718		885

Stock-Based Compensation

Fair Value Of Financial Instruments

New Accounting Guidance

Summary Of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2015

Summary Of Cash And Cash Equivalents

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



	December 31, 2015			December 31, 2014
(in thousands, except percentages)	Amount		% of Total	Amount		% of Total
Cash accounts	$	427,244	54.5	$	506,731	64.3
Money market mutual funds	356,924		45.5	281,333		35.7
Total	$	784,168		$	788,064

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)	2015		2014		2013
Net income	$	252,521	$	254,690	$	245,327
Weighted average shares outstanding – basic	89,561		92,067		92,691
Dilutive effect of stock plans	1,941		2,127		2,448
Weighted average shares outstanding – diluted	91,502		94,194		95,139
Basic earnings per share	$	2.82	$	2.77	$	2.65
Diluted earnings per share	$	2.76	$	2.70	$	2.58
Anti-dilutive options	206		718		885

Customer Concentration Risk [Member]

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)	2015		2014		2013
Revenue from channel partners	24	%	25	%	25	%
Largest channel partner	5	%	4	%	6	%
2^nd largest channel partner	2	%	2	%	2	%

Credit Concentration Risk [Member]

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)	2015		2014
Cash and cash equivalents held domestically	$	539,031	$	556,328
Cash and cash equivalents held by foreign subsidiaries	245,137		231,736
Cash and cash equivalents held in excess of deposit insurance, foreign and domestic	763,400		747,911
Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic	440,650		350,628

Acquisitions (Tables) - SpaceClaim Corporation [Member]

12 Months Ended

Dec. 31, 2015

Business Acquisition [Line Items]

Fair Value of Consideration Transferred

Fair Value of Consideration Transferred:



(in thousands)
Cash	$	84,892
ANSYS replacement stock options	68
Total consideration transferred at fair value	$	84,960

Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed

Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed:



(in thousands)
Cash	$	723
Accounts receivable and other tangible assets	1,857
Developed technology (10-year life)	15,800
Customer relationships (6-year life)	9,400
Trade name (6-year life)	1,300
Contract backlog (6-year life)	550
Non-compete agreement (2-year life)	300
Net deferred tax assets	9,288
Accounts payable and other liabilities	(2,011		)
Deferred revenue	(700		)
Total identifiable net assets	$	36,507
Goodwill	$	48,453

Other Receivables and Current Assets Other Receivables and Current Assets (Tables)

12 Months Ended

Dec. 31, 2015

Schedule of Other Receivables and Current Assets

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



(in thousands)	December 31, 2015		December 31, 2014
Receivables related to unrecognized revenue	$	170,186	$	152,830
Income taxes receivable, including overpayments and refunds	7,877		18,276
Prepaid expenses and other current assets	22,170		21,202
Total other receivables and current assets	$	200,233	$	192,308

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2015

Property, Plant and Equipment [Abstract]

Components Of Property and Equipment

Property and equipment consists of the following:



		December 31,
(in thousands)	Estimated Useful Lives	2015			2014
Equipment	1-10 years	$	78,932		$	75,500
Computer software	1-5 years	33,710			30,007
Buildings	10-40 years	25,041			24,526
Leasehold improvements	1-15 years	12,621			10,368
Furniture	1-13 years	8,601			8,475
Land		1,759			2,140
Property and equipment, gross		160,664			151,016
Less: Accumulated depreciation		(98,740		)	(86,373		)
Property and equipment, net		$	61,924		$	64,643

Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2015

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, 2015					December 31, 2014
(in thousands)	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
Finite-lived intangible assets:
Developed software and core technologies (3 – 11 years)	$	336,262	$	(251,201	)	$	321,076	$	(227,298	)
Customer lists and contract backlog (5 – 15 years)	159,885		(76,160		)	221,159		(121,380		)
Trade names (2 – 10 years)	127,903		(76,493		)	114,432		(63,082		)
Non-compete agreement	—		—			300		(52		)
Total	$	624,050	$	(403,854	)	$	656,967	$	(411,812	)
Indefinite-lived intangible assets:
Trade names	$	357				$	14,157

Estimated Future Amortization Expense for Intangible Assets

As of December 31, 2015, estimated future amortization expense for the intangible assets reflected above is as follows:



(in thousands)
2016	$	50,574
2017	47,714
2018	34,368
2019	20,887
2020	19,787
Thereafter	46,866
Total intangible assets subject to amortization	220,196
Indefinite-lived trade name	357
Other intangible assets, net	$	220,553

Changes in Goodwill

The changes in goodwill during the years ended December 31, 2015 and 2014 are as follows:



(in thousands)	2015			2014
Beginning balance - January 1	$	1,312,182		$	1,255,704
Acquisitions	28,561			60,484
Adjustments⁽¹⁾	(4,573		)	619
Currency translation	(3,822		)	(4,625		)
Ending balance - December 31	$	1,332,348		$	1,312,182

Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2015

Debt Disclosure [Abstract]

Interest Expense on Term Loan and Amortization Related to Debt Financing Costs

The interest expense on the term loan and amortization related to debt financing costs were as follows:



	Year Ended December 31, 2013
(in thousands)	Interest Expense		Amortization
July 31, 2008 term loan	$	230	$	149

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Fair Value of Assets and Liabilities Measured on Recurring Basis

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



				Fair Value Measurements at Reporting Date Using:
(in thousands)	December 31, 2015			Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents	$	356,924		$	356,924	$	—	$	—
Short-term investments	$	446		$	—	$	446	$	—
Liabilities
Contingent consideration	$	(1,376	)	$	—	$	—	$	(1,376	)



				Fair Value Measurements at Reporting Date Using:
(in thousands)	December 31, 2014			Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents	$	281,333		$	281,333	$	—	$	—
Short-term investments	$	714		$	—	$	714	$	—
Liabilities
Contingent consideration	$	(2,621	)	$	—	$	—	$	(2,621	)

Changes in Level 3 Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs



	Fair Value Measurement Using Significant Unobservable Inputs
(in thousands)	Contingent Consideration			Deferred Compensation
Balance as of January 1, 2014	$	7,389		$	704
Contingent payments	(4,866		)	(712		)
Interest expense and foreign exchange activity included in earnings	98			8
Balance as of December 31, 2014	$	2,621		$	—
Contingent payments	(1,456		)	—
Interest expense and foreign exchange activity included in earnings	211			—
Balance as of December 31, 2015	$	1,376		$	—

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Components Of Income Before Income Taxes

Income before income taxes includes the following components:



	Year Ended December 31,
(in thousands)	2015		2014		2013
Domestic	$	325,097	$	291,042	$	272,569
Foreign	31,668		57,097		49,920
Total	$	356,765	$	348,139	$	322,489

Components Of Provision For Income Taxes

The provision for income taxes is composed of the following:



	Year Ended December 31,
(in thousands)	2015			2014			2013
Current:
Federal	$	93,853		$	80,620		$	69,268
State	7,733			7,192			7,197
Foreign	17,854			24,495			24,722
Deferred:
Federal	(14,472		)	(18,536		)	(23,438		)
State	(1,987		)	(1,915		)	(2,187		)
Foreign	1,263			1,593			1,600
Total	$	104,244		$	93,449		$	77,162

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,
	2015		2014		2013
Federal statutory tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal benefit	1.1		1.2		1.1
Stock-based compensation	—		0.6		0.9
Net benefit of unrepatriated earnings	—		(0.3	)	(0.9	)
Uncertain tax positions	(0.4	)	(0.9	)	(3.7	)
Research and development credits	(1.1	)	(1.1	)	(2.0	)
Benefit from restructuring activities	(2.7	)	(4.1	)	(2.8	)
Domestic production activity benefit	(3.1	)	(3.5	)	(3.3	)
Other	0.4		(0.1	)	(0.4	)
	29.2	%	26.8	%	23.9	%

Components Of Deferred Tax Assets And Liabilities

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



	December 31,
(in thousands)	2015			2014
Deferred tax assets:
Net operating loss carryforwards	$	40,939		$	42,060
Stock-based compensation	23,258			23,331
Employee benefits	17,044			20,034
Uncertain tax positions	10,233			8,545
Deferred revenue	8,603			6,533
Research and development credits	3,562			4,349
Allowance for doubtful accounts	1,888			1,806
Other	3,240			2,877
Valuation allowance	(603		)	(130		)
	108,164			109,405
Deferred tax liabilities:
Other intangible assets	(73,933		)	(92,703		)
Property and equipment	(3,426		)	(4,652		)
	(77,359		)	(97,355		)
Net deferred tax assets	$	30,805		$	12,050

Reconciliation Of Unrecognized Tax Benefits

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



	Year Ended December 31,
(in thousands)	2015			2014			2013
Unrecognized tax benefit as of January 1	$	16,342		$	19,590		$	37,203
Gross increases—tax positions in prior period	64			488			320
Gross decreases—tax positions in prior period	(850		)	(3,715		)	(18,058		)
Gross increases—tax positions in current period	4,064			2,513			2,036
Reductions due to a lapse of the applicable statute of limitations	(2,808		)	(1,924		)	(1,734		)
Changes due to currency fluctuation	(653		)	(610		)	20
Settlements	(92		)	—			(197		)
Unrecognized tax benefit as of December 31	$	16,067		$	16,342		$	19,590

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

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, 2015, 2014 and 2013 is as follows:



	Year Ended December 31,
(in thousands, except per share amounts)	2015			2014			2013
Cost of sales:
Software licenses	$	745		$	1,776		$	1,349
Maintenance and service	1,868			2,035			2,293
Operating expenses:
Selling, general and administrative	17,153			17,073			16,847
Research and development	14,185			15,977			14,809
Stock-based compensation expense before taxes	33,951			36,861			35,298
Related income tax benefits	(11,656		)	(10,927		)	(11,096		)
Stock-based compensation expense, net of taxes	$	22,295		$	25,934		$	24,202
Net impact on earnings per share:
Basic earnings per share	$	(0.25	)	$	(0.28	)	$	(0.26	)
Diluted earnings per share	$	(0.24	)	$	(0.28	)	$	(0.25	)

Summary Of Stock Options

Information regarding stock option transactions is summarized below:



	Year Ended December 31,
	2015				2014				2013
(options in thousands)	Options		Weighted- Average Exercise Price		Options		Weighted- Average Exercise Price		Options		Weighted- Average Exercise Price
Outstanding, beginning of year	4,932		$	48.76	6,166		$	44.77	7,122		$	42.85
Granted	57		$	88.10	150		$	81.09	103		$	81.87
Issued pursuant to acquisitions	8		$	12.26	21		$	23.26	—		$	—
Exercised	(975	)	$	40.52	(1,266	)	$	31.36	(993	)	$	34.26
Forfeited	(36	)	$	70.15	(139	)	$	61.11	(66	)	$	53.75
Outstanding, end of year	3,986		$	51.07	4,932		$	48.76	6,166		$	44.77
Vested and Exercisable, end of year	3,539		$	48.29	3,958		$	44.22	4,351		$	38.18



	2015		2014		2013
Weighted-Average Remaining Contractual Term (in years)
Outstanding	4.85		5.53		5.99
Vested and Exercisable	4.53		5.00		5.13
Aggregate Intrinsic Value (in thousands)
Outstanding	$	165,131	$	163,932	$	261,601
Vested and Exercisable	$	156,487	$	149,536	$	213,304

Information Regarding Stock Options Outstanding

Information regarding stock options outstanding as of December 31, 2015 is summarized below:



(options in thousands)	Options Outstanding				Options Exercisable
Range of Exercise Prices	Options	Weighted- Average Remaining Contractual Life (years)	Weighted- Average Exercise Price		Options	Weighted- Average Exercise Price
$5.91 - $38.75	1,030	2.49	$	29.68	1,019	$	29.81
$38.86 - $48.97	1,077	4.27	$	45.39	1,077	$	45.39
$51.52 - $65.72	802	5.64	$	58.68	794	$	58.64
$67.34 - $94.15	1,077	7.08	$	71.55	649	$	69.43

Stock Options [Member]

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 each respective year:



	Year Ended December 31,
	2015	2014	2013
Risk-free interest rate	1.18% to 1.65%	1.49% to 1.76%	0.68% to 1.48%
Expected dividend yield	—%	—%	—%
Expected volatility	25%	35%	37%
Expected term	5.6 years	5.7 years	5.8 years
Weighted-average fair value per share	$30.83	$32.26	$29.85

Restricted Stock Units (RSUs) [Member]

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

Assumptions To Estimate Fair Value Of Stock Awards



	Year Ended December 31,
Assumptions used in Monte Carlo lattice pricing model	2015	2014	2013
Risk-free interest rate	1.1%	0.7%	0.4%
Expected dividend yield	—%	—%	—%
Expected volatility—ANSYS stock price	23%	25%	25%
Expected volatility—NASDAQ Composite Index	14%	15%	20%
Expected term	2.8 years	2.8 years	2.8 years
Correlation factor	0.60	0.70	0.70

Stock Repurchase Program Stock Repurchase Program (Tables)

12 Months Ended

Dec. 31, 2015

Equity, Class of Treasury Stock [Line Items]

Class of Treasury Stock

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



	Year Ended December 31,
(in thousands, except per share data)	2015		2014		2013
Number of shares repurchased	3,833		2,977		1,494
Average price paid per share	$	88.16	$	78.54	$	77.73
Total cost	$	337,910	$	233,793	$	116,132

Leases Leases (Tables)

12 Months Ended

Dec. 31, 2015

Operating Leased Assets [Line Items]

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, 2015 are as follows:



(in thousands)	Total		2016		2017		2018		2019		2020		Thereafter
Future minimum lease payments	$	71,887	$	13,800	$	10,449	$	7,834	$	7,043	$	6,195	$	26,566

Geographic Information (Tables)

12 Months Ended

Dec. 31, 2015

Segment Reporting [Abstract]

Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area

Revenue by geographic area is as follows:



	Year Ended December 31,
(in thousands)	2015		2014		2013
United States	$	354,433	$	320,327	$	292,323
Japan	104,299		108,757		108,064
Germany	94,546		99,714		93,525
South Korea	55,142		55,606		43,585
France	49,444		58,785		56,310
Canada	13,314		14,034		14,163
Other European	145,985		159,011		145,304
Other international	125,590		119,787		107,986
Total revenue	$	942,753	$	936,021	$	861,260

Schedule of Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries by Country

Property and equipment by geographic area is as follows:



	December 31,
(in thousands)	2015		2014
United States	$	47,971	$	49,957
Europe	6,808		7,840
India	3,286		3,123
Other international	3,859		3,723
Total property and equipment	$	61,924	$	64,643

Organization - Additional Information (Detail)	12 Months Ended
Organization - Additional Information (Detail)	Dec. 31, 2015 Segment
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]
Number of operating segments	1

Summary Of Significant Accounting Policies (Narrative) (Details) number in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Amortization	$ 58,149	$ 61,041	$ 60,700
Provisions for doubtful accounts	1,304	2,104	1,465
Net foreign exchange gains (losses)	486	(1,649)	$ (1,115)
Reclassification of certain deferred taxes to long-term deferred tax assets	32,896	28,240
Reclassification of certain deferred taxes to long-term deferred tax liabilities	$ 2,091	$ 16,190
Minimum [Member]
Frequency period of major product upgrades (months)	12 months
Semiconductor product licenses, term	24 months
Property and equipment, estimated useful lives (years)	1 year
Maximum [Member]
Frequency period of major product upgrades (months)	18 months
Semiconductor product licenses, term	36 months
Property and equipment, estimated useful lives (years)	40 years
Customer Concentration Risk [Member]
Number of customers with more than five percent of revenue	0	0	0
Adjustments for New Accounting Pronouncement [Member]
Reclassification of certain deferred taxes to long-term deferred tax assets		$ 7,000
Reclassification of certain deferred taxes to long-term deferred tax liabilities		$ 21,200

Summary Of Significant Accounting Policies (Summary Of Cash And Cash Equivalents) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Cash accounts	$ 427,244	$ 506,731
Money market mutual funds	356,924	281,333
Cash and cash equivalents	$ 784,168	$ 788,064	$ 742,486	$ 576,703
Cash accounts, % of Total	54.50%	64.30%
Money market mutual funds, % of Total	45.50%	35.70%

Summary Of Significant Accounting Policies (Schedule Of Risk Concentration) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Concentration Risk [Line Items]
Cash and cash equivalents, at carrying value	$ 784,168	$ 788,064	$ 742,486	$ 576,703
Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	24.20%	24.90%	25.30%
Number of customers with more than five percent of revenue	0	0	0
Credit Concentration Risk [Member]
Concentration Risk [Line Items]
Cash and cash equivalents held in excess of deposit insurance, foreign and domestic	$ 763,400	$ 747,911
Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic	$ 440,650	$ 350,628
1st Largest Channel Partner [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	5.00%	4.00%	6.00%
2nd Largest Channel Partner [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	2.00%	2.00%	2.00%
United States \| Credit Concentration Risk [Member]
Concentration Risk [Line Items]
Cash and cash equivalents, at carrying value	$ 539,031	$ 556,328
FOREIGN \| Credit Concentration Risk [Member]
Concentration Risk [Line Items]
Cash and cash equivalents, at carrying value	$ 245,137	$ 231,736

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, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Net income	$ 252,521	$ 254,690	$ 245,327
Weighted average shares outstanding - basic	89,561	92,067	92,691
Dilutive effect of stock plans	1,941	2,127	2,448
Weighted average shares outstanding - diluted	91,502	94,194	95,139
Basic earnings per share (in USD per share)	$ 2.82	$ 2.77	$ 2.65
Diluted earnings per share (in USD per share)	$ 2.76	$ 2.70	$ 2.58
Anti-dilutive options	206	718	885

- Definition

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

+ References + Details

- Definition

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

+ References + Details

Acquisition - Additional Information (Detail) - USD ($) $ in Thousands				12 Months Ended
	Apr. 30, 2014	Jan. 03, 2014	Apr. 03, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill				$ 1,332,348	$ 1,312,182	$ 1,255,704
Contingent consideration				1,376	2,621
Contingent consideration, installment payments				1,173	4,504	$ 3,174
2015 Other Acquisitions [Member]
Business Acquisition [Line Items]
Total consideration transferred at fair value				49,700
Finite-lived intangibles				24,500
Goodwill				27,500
Business combination, historical carrying value of acquired deferred revenue				900
Acquired deferred revenue, impact on reported revenue				826
Acquired deferred revenue, expected impact on reported revenue in next fiscal year				102
SpaceClaim Corporation [Member]
Business Acquisition [Line Items]
Total consideration transferred at fair value	$ 84,960
Goodwill				48,453
Business combination, historical carrying value of acquired deferred revenue	3,300
Acquired deferred revenue, impact on reported revenue				635	2,000
Goodwill, period increase (decrease)				(4,800)
Deferred revenue				(700)
Cash payments for acquisitions	$ 84,892
Reaction Design [Member]
Business Acquisition [Line Items]
Total consideration transferred at fair value		$ 19,100
Finite-lived intangibles				7,000
Goodwill				9,200
Business combination, historical carrying value of acquired deferred revenue		$ 2,300
Acquired deferred revenue, impact on reported revenue				264	$ 2,000
Goodwill, period increase (decrease)				1,900
Noncontrolling interest, period decrease				(600)
EVEN-Evolutionary Engineering Aktiengesellschaft [Member]
Business Acquisition [Line Items]
Total consideration transferred at fair value			$ 8,100
Finite-lived intangibles				$ 2,600
Finite-lived intangible asset, useful life				5 years
Goodwill				$ 5,900
Cash payments for acquisitions			4,500
Contingent consideration			$ 3,597
Contingent consideration, installment payments				$ 3,000
Minimum [Member] \| 2015 Other Acquisitions [Member]
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life				5 years
Minimum [Member] \| Reaction Design [Member]
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life				2 years
Maximum [Member] \| 2015 Other Acquisitions [Member]
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life				10 years
Maximum [Member] \| Reaction Design [Member]
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life				11 years

Fair Value of Consideration Transferred (Detail) - USD ($) $ in Thousands		12 Months Ended
	Apr. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
ANSYS replacement stock options		$ 3,528	$ 68	$ 0
SpaceClaim Corporation [Member]
Business Acquisition [Line Items]
Cash payments for acquisitions	$ 84,892
ANSYS replacement stock options	68
Total consideration transferred at fair value	$ 84,960

Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Combination, Separately Recognized Transactions [Line Items]
Goodwill	$ 1,332,348	$ 1,312,182	$ 1,255,704
SpaceClaim Corporation [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Cash	723
Accounts receivable and other tangible assets	1,857
Deferred tax assets	9,288
Accounts payable and other liabilities	(2,011)
Deferred revenue	(700)
Total identifiable net assets	36,507
Goodwill	48,453
SpaceClaim Corporation [Member] \| Developed Software
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangibles	15,800
SpaceClaim Corporation [Member] \| Customer Relationships
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangibles	9,400
SpaceClaim Corporation [Member] \| Trade Names
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangibles	1,300
SpaceClaim Corporation [Member] \| Contract Backlog
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangibles	550
SpaceClaim Corporation [Member] \| Non-Compete Agreements
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangibles	$ 300

Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed Estimated Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2015
SpaceClaim Corporation [Member] \| Developed Software
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible asset, useful life	10 years
SpaceClaim Corporation [Member] \| Customer Relationships
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible asset, useful life	6 years
SpaceClaim Corporation [Member] \| Trade Names
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible asset, useful life	6 years
SpaceClaim Corporation [Member] \| Contract Backlog
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible asset, useful life	6 years
SpaceClaim Corporation [Member] \| Non-Compete Agreements
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible asset, useful life	2 years
EVEN-Evolutionary Engineering Aktiengesellschaft [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible asset, useful life	5 years
Maximum [Member] \| Trade Names
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible asset, useful life	10 years
Maximum [Member] \| Reaction Design [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible asset, useful life	11 years
Minimum [Member] \| Trade Names
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible asset, useful life	2 years
Minimum [Member] \| Reaction Design [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Finite-lived intangible asset, useful life	2 years

Other Receivables and Current Assets - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Other receivables and current assets	$ 200,233	$ 192,308
Receivables related to unrecognized revenue
Other receivables and current assets	170,186	152,830
Income taxes receivable, including overpayments and refunds
Other receivables and current assets	7,877	18,276
Prepaid expenses and other current assets
Other receivables and current assets	$ 22,170	$ 21,202

Property and Equipment (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Abstract]
Depreciation expense related to property and equipment	$ 19.5	$ 20.9	$ 19.9

Property and Equipment (Components Of Property and Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 160,664	$ 151,016
Less: Accumulated depreciation	(98,740)	(86,373)
Property and equipment, net	61,924	64,643
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	78,932	75,500
Computer Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	33,710	30,007
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, gross	25,041	24,526
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	12,621	10,368
Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,601	8,475
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,759	$ 2,140
Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum [Member] \| Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum [Member] \| Computer Software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum [Member] \| Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	10 years
Minimum [Member] \| Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Minimum [Member] \| Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	1 year
Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	40 years
Maximum [Member] \| Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	10 years
Maximum [Member] \| Computer Software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	5 years
Maximum [Member] \| Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	40 years
Maximum [Member] \| Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	15 years
Maximum [Member] \| Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	13 years

Intangible Assets and Estimated Useful Lives (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	$ 624,050	$ 656,967
Amortized intangible assets, accumulated amortization	(403,854)	(411,812)
Unamortized intangible assets, gross carrying amount	357
Developed Software and Core Technologies
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	336,262	321,076
Amortized intangible assets, accumulated amortization	(251,201)	(227,298)
Customer Lists and Contract Backlog
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	159,885	221,159
Amortized intangible assets, accumulated amortization	(76,160)	(121,380)
Trade Names
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	127,903	114,432
Amortized intangible assets, accumulated amortization	(76,493)	(63,082)
Non-Compete Agreements
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	0	300
Amortized intangible assets, accumulated amortization	0	(52)
Trade Names
Intangible Assets [Line Items]
Unamortized intangible assets, gross carrying amount	$ 357	$ 14,157

Intangible Assets and Estimated Useful Lives	12 Months Ended
Intangible Assets and Estimated Useful Lives	Dec. 31, 2015
Developed Software and Core Technologies \| Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	3 years
Developed Software and Core Technologies \| Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	11 years
Customer Lists and Contract Backlog \| Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	5 years
Customer Lists and Contract Backlog \| Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	15 years
Trade Names \| Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	2 years
Trade Names \| Maximum [Member]
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, 2015	Dec. 31, 2014	Dec. 31, 2013
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization	$ 58,149	$ 61,041	$ 60,700

Estimated Future Amortization Expense for Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
2016	$ 50,574
2017	47,714
2018	34,368
2019	20,887
2020	19,787
Thereafter	46,866
Total intangible assets subject to amortization	220,196
Indefinite-lived trade names	357
Other intangible assets, net	$ 220,553	$ 259,312

Changes in Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
Changes in Goodwill (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Roll Forward]
Beginning balance	$ 1,312,182	$ 1,255,704
Acquisitions	28,561	60,484
Adjustments	(4,573)	619
Currency translation	(3,822)	(4,625)
Ending balance	$ 1,332,348	$ 1,312,182

Long-Term Debt - Additional Information (Detail)	12 Months Ended
Long-Term Debt - Additional Information (Detail)	Dec. 31, 2013
Debt Instrument [Line Items]
Interest rate on term loan	1.04%

Interest Expense on Term Loan and Amortization Related to Debt Financing Costs (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2013 USD ($)
Debt Instrument [Line Items]
Interest expense	$ 230
Amortization	$ 149

Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 356,924	$ 281,333
Short-term investments	446	714
Contingent consideration	(1,376)	(2,621)
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	356,924	281,333
Short-term investments	0	0
Contingent consideration	0	0
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	446	714
Contingent consideration	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
Contingent consideration	$ (1,376)	$ (2,621)

Fair Value Measurement - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments maturity	3 months
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments maturity	1 year

Changes in Level 3 Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Detail) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Contingent Consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 2,621	$ 7,389
Contingent payments	(1,456)	(4,866)
Interest expense and foreign exchange activity included in earnings	211	98
Ending balance	1,376	2,621
Deferred Compensation
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	0	704
Contingent payments	0	(712)
Interest expense and foreign exchange activity included in earnings	0	8
Ending balance	$ 0	$ 0

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2013	Dec. 31, 2014
Income Tax Contingency [Line Items]
Amount in excess of the amount for financial reporting over the tax bases	$ 202,900
Deferred tax liabilities, undistributed foreign earnings	20,900
Deferred tax assets, operating loss carryforwards, foreign	9,300
Deferred tax assets, valuation allowance	603		$ 130
Valuation allowance, deferred tax asset, increase, amount	700
Deferred tax assets, operating loss carryforwards, state and local	1,600
Tax credit carryforwards	4,700
Tax benefit from effective settlement of 2009 and 2010 refund claims		$ 11,000
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit	400
Unrecognized tax benefits that would impact effective tax rate	10,500
Liability for penalties	1,900		1,600
Liability for interest	2,700		$ 2,700
Subject To Expiration [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	4,000
Not Subject To Expiration [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	700
Foreign Country [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	84,000
Foreign Country [Member] \| Subject To Expiration [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	54,600
Federal Domestic [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	40,800
Operating Loss Carryforward With No Expiration Date [Member] \| Foreign Country [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	29,400
Subject To Utilization Limitations [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	$ 3,000
Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Tax credit carryforward, expiration date	Jan. 01, 2016
Earliest Tax Year [Member] \| Foreign Country [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Jan. 01, 2019
Earliest Tax Year [Member] \| Federal Domestic [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Jan. 01, 2020
Earliest Tax Year [Member] \| State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Jan. 01, 2016
Latest Tax Year [Member]
Income Tax Contingency [Line Items]
Tax credit carryforward, expiration date	Dec. 31, 2035
Years open to examination	2015
Latest Tax Year [Member] \| Foreign Country [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2025
Latest Tax Year [Member] \| Federal Domestic [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2034
Latest Tax Year [Member] \| State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2035
Tax Year 2013 [Member]
Income Tax Contingency [Line Items]
Years open to examination	2013
Tax Year 2014 [Member]
Income Tax Contingency [Line Items]
Years open to examination	2014
Valuation Allowance, Operating Loss Carryforwards [Member] \| Foreign Country [Member]
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance	$ 9,300

Income Taxes (Components Of Income Before Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Domestic	$ 325,097	$ 291,042	$ 272,569
Foreign	31,668	57,097	49,920
Income before income tax provision	$ 356,765	$ 348,139	$ 322,489

Income Taxes (Components Of Provision For Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Current, Federal	$ 93,853	$ 80,620	$ 69,268
Current, State	7,733	7,192	7,197
Current, Foreign	17,854	24,495	24,722
Deferred, Federal	(14,472)	(18,536)	(23,438)
Deferred, State	(1,987)	(1,915)	(2,187)
Deferred, Foreign	1,263	1,593	1,600
Total	$ 104,244	$ 93,449	$ 77,162

Income Taxes (Reconciliation Of U.S. Federal Statutory Tax Rate To Consolidated Effective Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal statutory tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefit	1.10%	1.20%	1.10%
Stock-based compensation	0.00%	0.60%	0.90%
Net benefit of unrepatriated earnings	0.00%	(0.30%)	(0.90%)
Uncertain tax positions	(0.40%)	(0.90%)	(3.70%)
Research and development credits	(1.10%)	(1.10%)	(2.00%)
Benefit from restructuring activities	(2.70%)	(4.10%)	(2.80%)
Domestic production activity benefit	(3.10%)	(3.50%)	(3.30%)
Other	0.40%	(0.10%)	(0.40%)
Consolidated effective tax rate	29.20%	26.80%	23.90%

Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 40,939	$ 42,060
Stock-based compensation	23,258	23,331
Employee benefits	17,044	20,034
Uncertain tax positions	10,233	8,545
Deferred revenue	8,603	6,533
Research and development credits	3,562	4,349
Allowance for doubtful accounts	1,888	1,806
Other	3,240	2,877
Valuation allowance	(603)	(130)
Deferred tax assets	108,164	109,405
Other intangible assets	(73,933)	(92,703)
Property and equipment	(3,426)	(4,652)
Deferred tax liabilities	(77,359)	(97,355)
Net deferred tax assets	$ 30,805	$ 12,050

Income Taxes (Reconciliation Of Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Unrecognized tax benefit as of January 1	$ 16,342	$ 19,590	$ 37,203
Gross increases-tax positions in prior period	64	488	320
Gross decreases-tax positions in prior period	(850)	(3,715)	(18,058)
Gross increases-tax positions in current period	4,064	2,513	2,036
Reductions due to a lapse of the applicable statute of limitations	(2,808)	(1,924)	(1,734)
Unrecognized tax benefits, decrease resulting from foreign currency translation	(653)	(610)
Unrecognized tax benefits, increase resulting from foreign currency translation			20
Settlements	(92)	0	(197)
Unrecognized tax benefit as of December 31	$ 16,067	$ 16,342	$ 19,590

Pension And Profit-Sharing Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Contribution Plan Disclosure [Line Items]
Expenses related to retirement programs	$ 8.4	$ 8.9	$ 8.0
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]
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 Of Employee Pay [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 (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares authorized for grant under the plan	30,400,000	30,400,000
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%
Expiration period of options from the date of grant		10 years
Expiration period for optionee who meets the 10% criteria		5 years
Vesting period		4 years
Maximum months after sale event where awards fully vest when service relationship terminated without cause		18 months
Maximum number of days that may be granted to terminated employee to exercise awards prior to termination			15 days
Share-based compensation arrangement by share-based payment award, options, vested in period, fair value		$ 12,300	$ 19,500	$ 24,700
Total unrecognized estimated compensation cost	$ 10,100	$ 10,100
Weighted-average period of recognition of unrecognized compensation cost (years)		1 year 5 months
Total intrinsic value of options exercised during the period		$ 47,100	60,600	45,200
Unvested options	400,000	400,000
Aggregate intrinsic value of unvested options	$ 9,200	$ 9,200
Weighted-average exercise price of unvested options	$ 73.13	$ 73.13
Weighted-average remaining contractual term of unvested stock options (years)		7 years 5 months
Employee service share-based compensation, cash received from exercise of stock options		$ 39,500
Tax benefit from exercise of stock options		17,700
Stock-based compensation expense		33,951	36,861	35,298
Fair value of stock options and restricted stock awards assumed in connection with acquisitions		$ 3,528	$ 68	$ 0
Performance Shares [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of performance-based restricted stock units granted		34,450	47,000	94,300
Value of the restricted stock units on the grant date	$ 81.61	$ 81.61	$ 65.94	$ 50.05
Stock-based compensation expense		$ 3,100	$ 2,500	$ 3,600
Deferred Stock Units [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock-based compensation expense		$ 4,000	$ 3,500	2,500
Restricted stock units earned	189,099	43,134
Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period		4 years
Number of performance-based restricted stock units granted		344,500	364,150
Value of the restricted stock units on the grant date	$ 86.34	$ 86.34	$ 82.13
Stock-based compensation expense		$ 12,500	$ 5,800
Restricted stock units earned		85,713
Share-based compensation arrangement by share-based payment award, equity instruments other than options, nonvested, number	571,462	571,462	344,750
Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Value of the restricted stock units on the grant date	$ 86.38	$ 86.38	$ 81.52
Stock-based compensation expense		$ 400	$ 100
Share-based compensation arrangement by share-based payment award, shares issued in period		51,795	20,667
2015 Other Acquisitions [Member] \| Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Value of the restricted stock units on the grant date	$ 90.48	$ 90.48
Stock-based compensation expense		$ 600
Share-based compensation arrangement by share-based payment award, shares issued in period		68,451
Stock issued during period, value, restricted stock award		$ 6,200
Apache Design Inc [Member] \| Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock-based compensation expense			$ 4,700	$ 3,800
Minimum [Member] \| Performance Shares [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period		1 year
Maximum [Member] \| Performance Shares [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period		3 years

Stock-Based Compensation (Summary Of Stock Options) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning of period, Weighted-Average Exercise Price	$ 48.76	$ 44.77	$ 42.85
Granted, Weighted-Average Exercise Price	88.10	81.09	81.87
Issued pursuant to acquisitions, Weighted-Average Exercise Price	12.26	23.26	0.00
Exercised, Weighted-Average Exercise Price	40.52	31.36	34.26
Forfeited, Weighted-Average Exercise Price	70.15	61.11	53.75
Outstanding, end of period, Weighted-Average Exercise Price	51.07	48.76	44.77
Vested and Exercisable, end of period, Weighted-Average Exercise Price	$ 48.29	$ 44.22	$ 38.18
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning of year, Options	4,932	6,166	7,122
Granted, Options	57	150	103
Issued pursuant to acquisitions, Options	8	21	0
Exercised, Options	(975)	(1,266)	(993)
Forfeited, Options	(36)	(139)	(66)
Outstanding, end of year, Options	3,986	4,932	6,166
Vested and Exercisable, end of year, Options	3,539	3,958	4,351
Outstanding, Weighted-Average Remaining Contractual Term (in years)	4 years 10 months 5 days	5 years 6 months 12 days	5 years 11 months 25 days
Vested and Exercisable, Weighted-Average Remaining Contractual Term (in years)	4 years 6 months 12 days	5 years	5 years 1 month 18 days
Outstanding, Aggregate Intrinsic Value	$ 165,131	$ 163,932	$ 261,601
Vested and Exercisable, Aggregate Intrinsic Value	$ 156,487	$ 149,536	$ 213,304

Stock-Based Compensation (Stock-Based Compensation Expense) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 33,951	$ 36,861	$ 35,298
Stock-based compensation expense	33,951	36,861	35,298
Related income tax benefits	(11,656)	(10,927)	(11,096)
Stock-based compensation expense, net of taxes	$ 22,295	$ 25,934	$ 24,202
Basic earnings per share	$ (0.25)	$ (0.28)	$ (0.26)
Diluted earnings per share	$ (0.24)	$ (0.28)	$ (0.25)
Software Licenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 745	$ 1,776	$ 1,349
Maintenance And Service [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	1,868	2,035	2,293
Selling, General And Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	17,153	17,073	16,847
Research And Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 14,185	$ 15,977	$ 14,809

Stock-Based Compensation (Assumptions To Estimate Fair Value Of Stock Awards) (Details)	12 Months Ended
	Dec. 31, 2015 $ / shares	Dec. 31, 2014 $ / shares	Dec. 31, 2013 $ / shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Risk-free interest rate, minimum	1.18%	1.49%	0.68%
Risk-free interest rate, maximum	1.65%	1.76%	1.48%
Expected dividend yield	0.00%	0.00%	0.00%
Expected volatility	25.00%	35.00%	37.00%
Expected term (in years)	5 years 7 months 7 days	5 years 8 months 7 days	5 years 9 months 6 days
Weighted-average fair value per share	$ 30.83	$ 32.26	$ 29.85
Restricted Stock Unit Compensation Expense [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
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
Risk-free interest rate	1.10%	0.70%	0.35%
Correlation factor	0.60	0.70	0.70
Restricted Stock Unit Compensation Expense [Member] \| ANSYS Stock Price [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility	23.00%	25.00%	25.00%
Restricted Stock Unit Compensation Expense [Member] \| NASDAQ Composite Index [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility	14.00%	15.00%	20.00%

Stock-Based Compensation (Information Regarding Stock Options Outstanding) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2015 $ / shares shares
$5.91 - $38.75
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	$ 38.75
Options Outstanding, Options \| shares	1,030
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	2 years 5 months 28 days
Options Outstanding, Weighted-Average Exercise Price	$ 29.68
Options Exercisable, Options \| shares	1,019
Options Exercisable, Weighted-Average Exercise Price	$ 29.81
$38.86 - $48.97
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	38.86
Range of Exercise Prices, Upper Limit	$ 48.97
Options Outstanding, Options \| shares	1,077
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	4 years 3 months 8 days
Options Outstanding, Weighted-Average Exercise Price	$ 45.39
Options Exercisable, Options \| shares	1,077
Options Exercisable, Weighted-Average Exercise Price	$ 45.39
$51.52 - $65.72
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	51.52
Range of Exercise Prices, Upper Limit	$ 65.72
Options Outstanding, Options \| shares	802
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	5 years 7 months 20 days
Options Outstanding, Weighted-Average Exercise Price	$ 58.68
Options Exercisable, Options \| shares	794
Options Exercisable, Weighted-Average Exercise Price	$ 58.64
$67.34 - $94.15
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	67.34
Range of Exercise Prices, Upper Limit	$ 94.15
Options Outstanding, Options \| shares	1,077
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	7 years 28 days
Options Outstanding, Weighted-Average Exercise Price	$ 71.55
Options Exercisable, Options \| shares	649
Options Exercisable, Weighted-Average Exercise Price	$ 69.43

Stock Repurchase Program - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 16, 2016
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased	3,833,000	2,977,000	1,494,000
Average price paid per share	$ 88.16	$ 78.54	$ 77.73
Total cost	$ 337,910	$ 233,793	$ 116,132
Remaining number of shares authorized to be repurchased under stock repurchase program	2,100,000
Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, number of shares authorized to be repurchased				5,000,000

Employee Stock Purchase Plan Employee Stock Purchase Plan (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized	30,400,000	30,400,000
Stock-based compensation expense		$ 33,951	$ 36,861	$ 35,298
Employee Stock \| ANSYS 1996 Employee Stock Purchase Plan [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized	1,600,000	1,600,000
Share-based compensation arrangement by share-based payment award, maximum employee subscription rate	10.00%	10.00%
Maximum number of shares per employee		3,840
Maximum employee subscription rate, value		$ 25
Share-based compensation arrangement by share-based payment award, shares issued in period	1,400,000
Stock-based compensation expense		$ 1,036	$ 876	$ 765
Maximum [Member] \| Employee Stock \| ANSYS 1996 Employee Stock Purchase Plan [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Eligibility, ownership percentage of voting power of all classes of stock of the company	5.00%	5.00%
Purchase price of common stock, percent		90.00%

Leases (Details) ft² in Thousands, $ in Thousands	12 Months Ended
Leases (Details) ft² in Thousands, $ in Thousands	Dec. 31, 2015 USD ($) ft²	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Operating Leased Assets [Line Items]
Lease rental expense incurred	$ 16,500	$ 15,800	$ 14,100
Future minimum lease payments	71,887
Future minimum lease payments, Year 1	13,800
Future minimum lease payments, Year 2	10,449
Future minimum lease payments, Year 3	7,834
Future minimum lease payments, Year 4	7,043
Future minimum lease payments, Year 5	6,195
Future minimum lease payments, Thereafter	$ 26,566
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	800
Amended Lease Agreement Effective January 1, 2004 \| Canonsburg Office
Operating Leased Assets [Line Items]
Lease rental expense incurred		$ 1,400	$ 1,400

Royalty Agreements (Details) - USD ($) $ in Millions	12 Months Ended
Royalty Agreements (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Royalty Agreements [Abstract]
Royalty fees reported in cost of goods sold	$ 11.8	$ 11.5	$ 10.3

Revenue by Geographic Area (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 942,753	$ 936,021	$ 861,260
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	354,433	320,327	292,323
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	104,299	108,757	108,064
Germany
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	94,546	99,714	93,525
South Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	55,142	55,606	43,585
France
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	49,444	58,785	56,310
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	13,314	14,034	14,163
Other European
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	145,985	159,011	145,304
Other International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 125,590	$ 119,787	$ 107,986

Property and Equipment by Geographic Area (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment	$ 61,924	$ 64,643
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment	47,971	49,957
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment	6,808	7,840
India
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment	3,286	3,123
Other International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment	$ 3,859	$ 3,723

Unconditional Purchase Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Unconditional Purchase Obligations (Excluding Capital Stock Redemptions) [Abstract]
Unconditional purchase obligations, beginning of year	$ 5,300	$ 2,900	$ 3,300
Future expenditures under purchase obligations, next twelve months	7,199
Future expenditures under purchase obligations, year two	1,301
Future expenditures under purchase obligations, year three	$ 688

Contingencies and Commitments - Additional Information (Detail) $ in Millions	Dec. 31, 2015 USD ($)
Maximum [Member]
Other Commitments And Contingencies [Line Items]
Tax charges and related liabilities if the ruling is unfavorable	$ 6

Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Movement in Valuation Allowances and Reserves [Roll Forward]
Provisions for doubtful accounts	$ 1,304	$ 2,104	$ 1,465
Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	5,500	5,700	4,800
Provisions for doubtful accounts	1,304	2,104	1,465
Deductions - returns and write-offs	1,604	2,304	565
Balance at end of year	$ 5,200	$ 5,500	$ 5,700