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Document And Entity Information - USD ($)	12 Months Ended
Document And Entity Information - USD ($)	Dec. 31, 2011	Feb. 16, 2012	Jun. 30, 2011
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2011
Document Fiscal Year Focus	2011
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 Voluntary Filers	No
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Public Float			$ 4,186,000,000
Entity Common Stock, Shares Outstanding		92,780,708

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 471,828	$ 472,479
Short-term investments	576	455
Accounts receivable, less allowance for doubtful accounts of $4,101 and $4,503, respectively	84,602	76,604
Other receivables and current assets	163,296	147,402
Deferred income taxes	19,731	17,693
Total current assets	740,033	714,633
Property and equipment, net	45,638	36,921
Goodwill	1,225,375	1,035,083
Other intangible assets, net	383,420	278,320
Other long-term assets	46,942	56,123
Deferred income taxes	7,062	5,796
Total assets	2,448,470	2,126,876
Current liabilities:
Current portion of long-term debt and capital lease obligations	74,423	31,962
Accounts payable	6,987	2,241
Accrued bonuses and commissions	36,164	29,719
Accrued income taxes	6,213	6,179
Deferred income taxes	0	216
Other accrued expenses and liabilities	55,809	41,247
Deferred revenue	259,155	199,805
Total current liabilities	438,751	311,369
Long-term liabilities:
Long-term debt and capital lease obligations, less current portion	53,149	127,563
Deferred income taxes	101,618	75,026
Other long-term liabilities	100,479	82,989
Total long-term liabilities	255,246	285,578
Commitments and contingencies	0	0
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; 92,651,739 and 91,647,012 shares issued and outstanding, respectively	927	916
Additional paid-in capital	905,662	856,718
Retained earnings	836,008	655,333
Accumulated other comprehensive income	11,876	16,962
Total stockholders' equity	1,754,473	1,529,929
Total liabilities and stockholders' equity	$ 2,448,470	$ 2,126,876

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 4,101	$ 4,503
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	92,651,739	91,647,012
Common stock, shares outstanding	92,651,739	91,647,012

Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenue:
Software licenses	$ 425,881	$ 351,033	$ 315,633
Maintenance and service	265,568	229,203	201,252
Total revenue	691,449	580,236	516,885
Cost of sales:
Software licenses	15,884	10,770	10,210
Amortization	33,728	32,757	36,011
Maintenance and service	69,402	57,352	50,021
Restructuring charges	0	0	994
Total cost of sales	119,014	100,879	97,236
Gross profit	572,435	479,357	419,649
Operating expenses:
Selling, general and administrative	180,357	155,096	137,264
Research and development	108,530	88,990	79,856
Amortization	17,989	16,003	16,326
Restructuring charges	0	0	2,726
Total operating expenses	306,876	260,089	236,172
Operating income	265,559	219,268	183,477
Interest expense	(3,332)	(4,488)	(10,401)
Interest income	3,000	1,911	1,740
Other expense, net	(369)	(297)	(1,287)
Income before income tax provision	264,858	216,394	173,529
Income tax provision	84,183	63,262	57,138
Net income	$ 180,675	$ 153,132	$ 116,391
Earnings per share-basic:
Basic earnings per share	$ 1.96	$ 1.69	$ 1.32
Weighted average shares-basic	92,120	90,684	88,486
Earnings per share-diluted:
Diluted earnings per share	$ 1.91	$ 1.64	$ 1.27
Weighted average shares-diluted	94,381	93,209	91,785

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net income	$ 180,675	$ 153,132	$ 116,391
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	65,955	60,826	64,186
Deferred income tax benefit	(3,021)	(26,641)	(28,038)
Provision for bad debts	404	1,757	1,610
Stock-based compensation expense	23,088	19,019	13,212
Excess tax benefits from stock options	(10,046)	(11,753)	(13,168)
Other	180	19	108
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	(8,086)	(11,149)	(6,434)
Other receivables and current assets	(16,926)	(61,467)	10,166
Other long-term assets	(1,390)	(60,365)	1,340
Accounts payable, accrued expenses and current liabilities	18,222	16,542	(7,016)
Accrued income taxes	9,668	10,608	19,929
Deferred revenue	49,973	28,817	(606)
Other long-term liabilities	(1,035)	47,539	2,009
Net cash provided by operating activities	307,661	166,884	173,689
Cash flows from investing activities:
Apache acquisition, net of cash acquired	(269,486)	0	0
Capital expenditures	(22,063)	(14,260)	(8,323)
Purchases of short-term investments	(351)	(1,075)	(9,899)
Maturities of short-term investments	257	8,687	7,491
Net cash used in investing activities	(291,643)	(6,648)	(10,731)
Cash flows from financing activities:
Principal payments on long-term debt	(31,889)	(65,630)	(53,924)
Principal payments on capital leases	(87)	(283)	(306)
Purchase of treasury stock	(12,704)	0	(39,904)
Proceeds from issuance of common stock under Employee Stock Purchase Plan	2,167	1,592	1,515
Proceeds from exercise of stock options	22,791	22,929	15,361
Excess tax benefits from stock options	10,046	11,753	13,168
Net cash used in financing activities	(9,676)	(29,639)	(64,090)
Effect of exchange rate fluctuations	(6,993)	6,004	8,834
Net (decrease) increase in cash and cash equivalents	(651)	136,601	107,702
Cash and cash equivalents, beginning of year	472,479	335,878	228,176
Cash and cash equivalents, end of year	471,828	472,479	335,878
Supplemental disclosures of cash flow information:
Income taxes paid	64,731	131,861	58,859
Interest paid	1,858	2,980	8,642
Capital lease obligations incurred	$ 0	$ 0	$ 96

Consolidated Statements Of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total Comprehensive Income [Member]	Total
Balance at Dec. 31, 2008	$ 897	$ 806,755	$ 385,810	$ (9,079)	$ (1,484)		$ 1,182,899
Balance, shares at Dec. 31, 2008	89,716,000			337,000
Treasury shares acquired				$ (39,904)			$ (39,904)
Treasury shares acquired, shares				2,070,000			2,069,763
Stock-based compensation activity, including tax benefit	$ 0	(5,118)		$ 46,552			$ 41,434
Stock-based compensation activity, including tax benefit, shares	0			(2,298,000)
Issuance of common stock under Employee Stock Purchase Plan	$ 0	(63)		$ 1,578			1,515
Issuance of common stock under Employee Stock Purchase Plan, shares	0			(68,000)
Net gains on interest rate swap, net of tax					1,959	$ 1,959	1,959
Other comprehensive gain (loss)					8,337	8,337	8,337
Net income for the year			116,391			116,391	116,391
Balance at Dec. 31, 2009	$ 897	801,574	502,201	$ (853)	8,812	126,687	$ 1,312,631
Balance, shares at Dec. 31, 2009	89,716,000			41,000
Treasury shares acquired, shares							0
Stock-based compensation activity, including tax benefit	$ 19	53,552		$ 853			$ 54,424
Stock-based compensation activity, including tax benefit, shares	1,883,000			(41,000)
Issuance of common stock under Employee Stock Purchase Plan	$ 0	1,592		$ 0			1,592
Issuance of common stock under Employee Stock Purchase Plan, shares	(48,000)			0
Net gains on interest rate swap, net of tax					532	532	532
Other comprehensive gain (loss)					7,618	7,618	7,618
Net income for the year			153,132			153,132	153,132
Balance at Dec. 31, 2010	$ 916	856,718	655,333	$ 0	16,962	161,282	1,529,929
Balance, shares at Dec. 31, 2010	91,647,000			0
Treasury shares acquired				$ (12,704)			$ (12,704)
Treasury shares acquired, shares				247,000			247,443
Stock-based compensation awards issued in Apache acquisition		3,170					$ 3,170
Stock-based compensation activity, including tax benefit	$ 10	43,608		$ 12,704			56,322
Stock-based compensation activity, including tax benefit, shares	955,000			(247,000)
Issuance of common stock under Employee Stock Purchase Plan	$ 1	2,166		$ 0			2,167
Issuance of common stock under Employee Stock Purchase Plan, shares	(50,000)			0
Other comprehensive gain (loss)					(5,086)	(5,086)	(5,086)
Net income for the year			180,675			180,675	180,675
Balance at Dec. 31, 2011	$ 927	$ 905,662	$ 836,008	$ 0	$ 11,876	$ 175,589	$ 1,754,473
Balance, shares at Dec. 31, 2011	92,652,000			0

Consolidated Statements Of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements Of Stockholders' Equity [Abstract]
Stock-based compensation activity, tax benefit	$ 9,984	$ 12,022	$ 12,679
Net gains on interest rate swap, tax		$ 321	$ 1,217

Organization	12 Months Ended
Organization	Dec. 31, 2011
Organization [Abstract]
Organization	1. 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, automotive, manufacturing, electronics, biomedical, energy and defense. In connection with its August 1, 2011 acquisition of Apache Design, Inc. ("Apache"), the Company has reviewed the accounting guidance issued for disclosures about segments of an enterprise. As defined by the accounting guidance, the Company operates as two segments. However, the Company determined that its two operating segments are sufficiently similar and should be aggregated under the criteria provided in the related accounting guidance. 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. As a result, it is impracticable for the Company to provide accurate historical or current reporting among its various product lines.

Summary Of Significant Accounting Policies

12 Months Ended

Dec. 31, 2011

Summary Of Significant Accounting Policies [Abstract]

Summary Of Significant Accounting Policies

2. Summary of Significant 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 and tax valuation reserves, fair value of stock-based compensation, contract revenue, useful lives for depreciation and amortization, loss contingencies, valuation of goodwill and indefinite lived intangible assets, contingent consideration and deferred compensation. 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 post-contract customer support ("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 license 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.

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 signed license agreement is received from the end user customer 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, and 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,

2011

2010

(in thousands, except percentages)

Amount

% of Total

Amount

% of Total

Cash accounts

289,298

61.3

170,765

36.1

Money market mutual funds

181,198

38.4

273,926

58.0

Time deposits

1,332

0.3

27,788

5.9

Total

471,828

472,479

The money market mutual fund balances reflected above are held in various funds of a single issuer. The time deposits balance at December 31, 2010 was primarily invested in pooled funds which held a mix of bank time deposits with varying durations of up to three months.

SHORT-TERM INVESTMENTS: Short-term investments consist primarily of deposits held by certain foreign subsidiaries of the Company with original maturities of three months to one year. The Company considers investments backed by government agencies or financial institutions with maturities of less than one year to be highly liquid and classifies such investments as short-term investments. Short-term investments are recorded at fair value. The Company uses the specific identification method to determine the realized gain or loss upon the sale of such securities.

The Company is averse to principal loss and seeks to preserve invested funds by limiting default risk, market risk and reinvestment risk by placing its investments with high-quality credit issuers.

PROPERTY AND EQUIPMENT: Property and equipment is stated at cost. Depreciation is computed on the straight-line method over the estimated useful lives of the various classes of assets, which range from one to 40 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 COSTS: Research and development costs, other than certain capitalized software development costs, are expensed as incurred.

CAPITALIZED SOFTWARE: Internally developed computer software costs and costs of product enhancements are capitalized subsequent to the determination of technological feasibility; such capitalization continues until the product becomes available for commercial release. Judgment is required in determining when technological feasibility of a product is established. The Company has determined that technological feasibility is reached after all high-risk development issues have been resolved through coding and testing. Generally, the time between the establishment of technological feasibility and commercial release of software is minimal, resulting in insignificant capitalization of internally developed software costs. Amortization of capitalized software costs, both for internally developed as well as for purchased software products, is computed on a product-by-product basis over the estimated economic life of the product, which is generally three years. Amortization is the greater of the amount computed using: (i) the ratio of the current year's gross revenue to the total current and anticipated future gross revenue for that product or (ii) the straight-line method over the estimated life of the product. Amortization expense related to capitalized and acquired software costs, including the related trademarks, was $33.7 million, $32.8 million and $36.0 million for the years ended December 31, 2011, 2010 and 2009, respectively.

The Company periodically reviews the carrying value of capitalized software. Impairments are recognized in the results of operations when the expected future undiscounted operating cash flow derived from the capitalized costs of internally developed software is less than the carrying value. No impairment charges have been required to date.

GOODWILL AND OTHER INTANGIBLE ASSETS: Goodwill represents the excess of the consideration transferred over the fair value of net identifiable assets acquired. Intangible assets consist of trademarks, customer lists, contract backlog, and acquired software and technology.

The Company evaluates, at least annually, the realizability of the carrying value of goodwill and indefinite lived intangible assets by comparing the carrying value of the asset (or, in the case of goodwill, the Company's reporting units) to its estimated fair value. The Company performs its annual goodwill and indefinite lived intangible assets impairment test on January 1 of each year unless there is an indicator that would require a test during the year. No impairment charges have been required to date.

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. No impairment charges have been required to date.

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, except customer data)*	2011			2010			2009
Revenue from channel partners		26	%		27	%		26	%
1^st largest channel partner		4	%		4	%		5	%
2^nd largest channel partner		3	%		3	%		3	%
Direct sale customers exceeding 5% of revenue		0			0			0

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 maintains certain cash and cash equivalent accounts that are currently insured by the Federal Deposit Insurance Corporation ("FDIC") up to $250,000 per depositor or the Securities Investor Protection Corporation ("SIPC") up to $500,000 per customer. As of December 31, 2011, the Company had cash and cash equivalent balances of $297.7 million held in the U.S. which were uninsured by the FDIC or SIPC, and $153.4 million of uninsured cash and cash equivalent balances held outside of the U.S. The Company held cash and cash equivalent balances with one U.S. financial institution as of December 31, 2011 in the amount of $227.5 million.

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 provided 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 $400,000, $1.8 million and $1.6 million for the years ended December 31, 2011, 2010 and 2009, 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 income tax assets in the future in excess of their net recorded amount, an adjustment to the valuation allowance would be recorded that would reduce 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 limitation 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 unrecognized tax benefits 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. Accounts receivable and intercompany balances in foreign currencies at year end 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. The Company recorded net foreign exchange losses of $430,000, $400,000 and $1.4 million for the years ended December 31, 2011, 2010 and 2009, 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 occur.

ACCUMULATED OTHER COMPREHENSIVE INCOME: Accumulated other comprehensive income is composed entirely of foreign currency translation adjustments.

EARNINGS PER SHARE: Basic earnings per share ("EPS") amounts are computed by dividing earnings by the 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)*	2011		2010		2009
Net income	$	180,675	$	153,132	$	116,391

Weighted average shares outstanding—basic		92,120		90,684		88,486

Dilutive effect of stock plans		2,261		2,525		3,299

Weighted average shares outstanding—diluted		94,381		93,209		91,785

Basic earnings per share	$	1.96	$	1.69	$	1.32
Diluted earnings per share	$	1.91	$	1.64	$	1.27
Anti-dilutive options		1,421		1,867		2,612

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. The carrying value of long-term debt is considered a reasonable estimate of fair value due to the variable interest rate underlying the Company's credit facility.

DERIVATIVE FINANCIAL INSTRUMENTS: As of December 31, 2009 and 2008 and through its maturity on June 30, 2010, the Company held a derivative financial instrument to manage interest rate risk. The Company accounted for this instrument as a cash flow hedge in accordance with derivative instruments and hedging activities accounting guidance, which requires that every derivative instrument be recorded on the balance sheet as either an asset or liability measured at its fair value as of the reporting date. This guidance also requires that changes in the Company's derivative fair value be recognized in earnings unless specific hedge accounting and documentation criteria are met. The Company recorded the effective portion of its derivative financial instrument in accumulated other comprehensive income on the consolidated balance sheets. Any ineffective portion or excluded portion of the designated cash flow hedge was recognized in earnings. The Company's cash flow hedge did not have an ineffective or excluded portion. The Company utilized the hypothetical derivative method to ensure the hedge was effective in offsetting variability in interest expense associated with its credit facility. The Company used the dollar offset method for calculating ineffectiveness by comparing the cumulative fair value of the swap to the cumulative fair value of the hypothetical derivative.

NEW ACCOUNTING GUIDANCE:

Fair Value Measurements: In May 2011, new accounting guidance was issued to provide a consistent definition of fair value and to ensure that the fair value measurement and disclosure requirements are similar between generally accepted accounting principles in the United States and International Financial Reporting Standards. The guidance changes certain fair value measurement principles and enhances the disclosure requirements, particularly for Level 3 fair value measurements. This guidance is effective for the Company beginning January 1, 2012. Management is in the process of evaluating the impact of adopting this guidance on the Company's consolidated financial statements.

Presentation of Comprehensive Income: In June 2011, new accounting guidance was issued regarding the presentation of comprehensive income in consolidated financial statements. This guidance requires that all non-owner changes in stockholders' equity be presented either in a single continuous statement of comprehensive income or in two separate but consecutive statements. The updated guidance eliminates the option to present components of other comprehensive income as part of the statement of changes in stockholders' equity. This guidance is effective for the Company beginning January 1, 2012. Management is in the process of evaluating the impact of adopting this guidance on the Company's consolidated financial statements.

Testing Goodwill for Impairment: In September 2011, new accounting guidance was issued regarding the requirement to test goodwill for impairment on at least an annual basis. Existing guidance requires that this test be performed by comparing the fair value of a reporting unit with its carrying amount, including goodwill (step one). If the fair value of a reporting unit is less than its carrying amount, then the second step of the test must be performed to measure the amount of the impairment loss, if any. Under the new guidance, an entity has the option to first assess qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, an entity determines it is not more likely than not that the fair value of a reporting unit is less than its carrying amount, then performing the two-step impairment test is unnecessary. However, if an entity concludes otherwise, then it is required to perform the first step of the two-step impairment test. This guidance is effective for the Company beginning January 1, 2012. Management is in the process of evaluating the impact of adopting this guidance on the Company's consolidated financial statements.

Acquisitions

12 Months Ended

Dec. 31, 2011

Acquisitions [Abstract]

Acquisitions

3. Acquisitions

On August 1, 2011, the Company completed its acquisition of Apache Design, Inc., a leading simulation software provider for advanced, low-power solutions in the electronics industry. Under the terms of the merger agreement, ANSYS acquired 100% of the outstanding shares of Apache for a purchase price of $314.0 million, which included $31.9 million in acquired cash and short-term investments on Apache's balance sheet, $3.2 million in ANSYS replacement stock option awards issued to holders of partially-vested Apache stock options and $9.5 million in contingent consideration that is based on the retention of a key member of Apache's management. The agreement also includes $13.0 million of performance equity awards for key members of management and employees, earned annually over a three-fiscal-year period beginning January 1, 2012. These awards will be accounted for outside of the business combination. The Company funded the transaction entirely with existing cash balances.

Apache's software enables engineers to design power-efficient devices while satisfying ever-increasing performance requirements. Engineers use Apache's products to design and simulate efficient, low-power integrated circuits for high-performance electronic products found in devices such as tablets, smartphones, LCD televisions, laptops and high end computer servers. The complementary combination is expected to accelerate development and delivery of new and innovative products to the marketplace while lowering design and engineering costs for customers.

The operating results of Apache have been included in the Company's consolidated financial statements since the date of acquisition, August 1, 2011. The acquired business contributed revenues of $14.5 million and a net loss of $4.2 million to the Company during the period from August 1, 2011 to December 31, 2011. During the year ended December 31, 2011, the Company incurred $2.1 million in acquisition-related costs. These costs are included in selling, general and administrative expenses in the Company's consolidated statement of income for the year ended December 31, 2011.

The merger agreement includes a contingent consideration arrangement that requires additional payments totaling $12.0 million to be paid by the Company in equal installments to the Apache stockholders and holders of vested Apache options on each of the first three anniversaries of the closing of the acquisition. To receive these payments, a key member of Apache's management must remain an employee of ANSYS on each of the first three anniversaries of the acquisition closing date. Management estimated that it was probable that all three payments would be made, and recorded the fair value of the contingent payments as a liability on the date of acquisition. The portion of contingent payments attributable to the key member of Apache management was determined to be compensation, and is accounted for outside of the business combination. The portion of the contingent payments attributable to other shareholders was determined to be contingent purchase price consideration and was estimated to be $9.5 million based on the net present value of the expected payments. Refer to Note 8 for a description of the valuation technique and inputs used to estimate the fair value of the contingent consideration.

Under the merger agreement, holders of partially-vested Apache options at the date of acquisition received options to purchase ANSYS shares of common stock based on an agreed-upon conversion ratio ("the Replacement Awards"). The value of the Replacement Awards attributable to pre-combination service was estimated to be $3.2 million at the acquisition date, and was included in the consideration transferred. The value of the Replacement Awards attributable to post-combination service will be recognized as stock-based compensation in earnings during the post-acquisition period.

In valuing deferred revenue on the Apache balance sheet as of the acquisition date, the Company applied the fair value provisions applicable to the accounting for business combinations. Although this acquisition accounting requirement had no impact on the Company's business or cash flow, the Company's reported revenue under accounting principles generally accepted in the United States, primarily for the first 12 months post-acquisition, will be less than what would otherwise have been reported by Apache absent the acquisition. Acquired deferred revenue of $10.1 million was recorded on the opening balance sheet. This amount was approximately $13.6 million lower than the historical carrying value. The impact on reported revenue for the year ended December 31, 2011 was $9.6 million, primarily in lease license revenue. The expected impact on reported revenue for the year ending December 31, 2012 is $3.4 million.

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

Fair Value of Consideration Transferred:


*(in thousands)*
Cash	$	301,306
Contingent consideration		9,501
ANSYS replacement stock options		3,170

Total consideration transferred at fair value	$	313,977

Recognized Amounts of Identifiable Assets Acquired and Liabilities Assumed:


*(in thousands)*
Cash and short-term investments	$	31,948
Accounts receivable and other tangible assets		6,011
Developed software (7-year life)		82,500
Customer relationships (15-year life)		36,100
Contract backlog (3-year life)		13,500
Platform trade names (indefinite-lives)		21,900
Apache trade name (6-year life)		2,100
Accounts payable and other liabilities		(16,646	)
Deferred revenue		(10,100	)
Net deferred tax liabilities		(44,283	)

Total identifiable net assets	$	123,030

Goodwill	$	190,947

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 Apache.The fair values of the assets acquired and liabilities assumed that are listed above are based on preliminary calculations and the estimates and assumptions for these items are subject to change as additional information is obtained during the measurement period (up to one year from the acquisition date). During the measurement period since the Apache acquisition date, the Company retrospectively increased the values of identifiable intangible assets by $2.3 million, and reduced the values of net deferred tax liabilities and goodwill by $1.9 million and $4.3 million, respectively. These adjustments were based on refinements to assumptions used in the preliminary valuation of intangible assets and new information obtained in the calculation of the net deferred tax liabilities.

The following unaudited pro forma information presents the 2010 and 2011 results of operations of the Company as if the acquisition had occurred on January 1, 2010. The unaudited pro forma results are not necessarily indicative of results that would have occurred had the acquisition been in effect for the periods presented, nor are they necessarily indicative of future results. The 2010 pro forma results are based on the year ended December 31, 2010 for ANSYS, as reported, combined with the year ended December 31, 2010 results of Apache. The 2011 pro forma results are based on ANSYS's stand-alone results for the year ended December 31, 2011 combined with Apache's results for the year ended December 31, 2011. The unaudited pro forma financial information for all periods presented includes the business combination accounting effects on amortization expense from acquired intangible assets, lost interest income on the cash paid for the acquisition and the related tax effects. The unaudited pro forma financial information excludes contingent payments, transaction costs, IPO-related costs incurred by Apache prior to the acquisition, expenses related to performance awards issued as part of the acquisition and the income statement effects of the acquisition accounting adjustment to deferred revenue. No pro forma adjustments were made to stock-based compensation expense previously recorded by Apache.


	Year Ended December 31,
*(in thousands, except per share data)*	2011		2010
	(Unaudited)		(Unaudited)
Total revenue	$	730,632	$	624,283
Net income	$	181,718	$	144,605
Earnings per share:
Basic	$	1.97	$	1.59

Diluted	$	1.93	$	1.55

Other Current Assets	12 Months Ended
Other Current Assets	Dec. 31, 2011
Other Current Assets [Abstract]
Other Current Assets	4. Other Current Assets The Company reports accounts receivable, related to the portion of annual lease licenses and software maintenance that has not yet been recognized as revenue, as a component of other receivables and current assets. These amounts totaled $112.8 million and $89.9 million as of December 31, 2011 and 2010, respectively. The Company reports income taxes receivable, including amounts related to overpayments and refunds, as a component of other receivables and current assets. These amounts totaled $36.0 million and $32.9 million as of December 31, 2011 and 2010, respectively.

Pension And Profit-Sharing Plans	12 Months Ended
Pension And Profit-Sharing Plans	Dec. 31, 2011
Pension And Profit-Sharing Plans [Abstract]
Pension And Profit-Sharing Plans	10. Pension and Profit-Sharing Plans The Company has a 401(k)/profit-sharing plan for all qualifying full-time domestic employees that permit 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 qualifying domestic employees of the Company's Apache subsidiary, which was acquired on August 1, 2011, also participate in a 401(k) plan. There is no matching employer contribution associated with this plan. The Company also maintains various defined contribution pension arrangements for its international employees. Expenses related to the Company's retirement programs were $5.3 million in 2011, $3.9 million in 2010 and $3.4 million in 2009.

Non-Compete And Employment Agreements	12 Months Ended
Non-Compete And Employment Agreements	Dec. 31, 2011
Non-Compete And Employment Agreements [Abstract]
Non-Compete And Employment Agreements	11. 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 and, where legally permitted, that 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 Chairman of its Board of Directors. In the event the Chairman is terminated without cause, his employment agreement provides for severance at an annual rate of $300,000 for the earlier of a period of one year after termination or when he accepts other employment. The Chairman is subject to a one-year restriction on competition following termination of employment under the circumstances described in the contract. 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 Repurchase Program	12 Months Ended
Stock Repurchase Program	Dec. 31, 2011
Stock Repurchase Program [Abstract]
Stock Repurchase Program	13. Stock Repurchase Program In October 2001, the Company announced that its Board of Directors had amended its common stock repurchase program to acquire up to an additional four million shares, or 16 million shares in total, under a program that was initially announced in February 2000. Under this program, the Company repurchased 247,443 shares at an average price per share of $51.34 during the year ended December 31, 2011. The Company repurchased 0 and 2,069,763 shares under this program during 2010 and 2009, respectively. As of December 31, 2011, 1.1 million shares remained authorized for repurchase under the program.

Employee Stock Purchase Plan	12 Months Ended
Employee Stock Purchase Plan	Dec. 31, 2011
Employee Stock Purchase Plan [Abstract]
Employee Stock Purchase Plan	14. 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 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 purchase no more than $25,000 worth of common stock in any calendar year. At December 31, 2011, 1,184,082 shares of common stock had been issued under the Purchase Plan, of which 1,134,377 were issued as of December 31, 2010. The total compensation expense recorded under the Purchase Plan during the years ended December 31, 2011, 2010 and 2009 was $650,000, $500,000 and $410,000, respectively.

Leases	12 Months Ended
Leases	Dec. 31, 2011
Leases [Abstract]
Leases	15. Leases In January 1996, the Company entered into a lease agreement with an unrelated third party for a new corporate office facility, in Canonsburg, Pennsylvania, which the Company occupied in February 1997. In May 2004, the Company entered into the first amendment to this lease agreement, effective January 1, 2004. The lease was extended from an original period of ten years, with an option for five additional years, to a period of 18 years from the inception date, with an option for five additional years. The Company incurred lease rental expense related to this facility of $1.3 million in each of the years ended December 31, 2011, 2010 and 2009. The future minimum lease payments are $1.4 million per annum from January 1, 2012 through December 31, 2014. The future minimum lease payments from January 1, 2015 through December 31, 2019 will be determined based on prevailing market rental rates at the time of the extension, if elected. The amended lease also provided for the lessor to reimburse the Company for up to $550,000 in building refurbishments completed through March 31, 2006. These amounts have been recorded as a reduction of lease expense over the remaining term of the lease. As part of the acquisition of Apache on August 1, 2011, the Company acquired certain leased office property, including executive offices, which comprise a 52,000 square foot office facility in San Jose, California. In March 2011, Apache entered into the second amendment to its existing lease agreement, effective March 14, 2011. The lease term was extended to October 31, 2015. Total required minimum payments under the operating lease will be $910,000 in 2012, $980,000 in 2013, $1.3 million in 2014 and $1.1 million in 2015. In August 2009, the Company extended the executive office space lease agreement in Pittsburgh, Pennsylvania for a period of approximately three years and ten months, commencing February 15, 2011 and expiring December 31, 2014. Total required minimum payments under the operating lease will be $570,000 per annum from January 1, 2012 through December 31, 2014. The Company has also entered into various noncancellable operating leases for equipment and office space, including the locations referenced above. Office space lease expense totaled $12.8 million, $11.5 million and $12.4 million for the years ended December 31, 2011, 2010 and 2009, respectively. Future minimum lease payments under noncancellable operating leases for office space in effect at December 31, 2011 are $12.0 million in 2012, $8.4 million in 2013, $7.5 million in 2014, $4.2 million in 2015 and $1.6 million in 2016.

Royalty Agreements	12 Months Ended
Royalty Agreements	Dec. 31, 2011
Royalty Agreements [Abstract]
Royalty Agreements	16. 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 $8.4 million, $6.8 million and $6.9 million for the years ended December 31, 2011, 2010 and 2009, respectively.

Unconditional Purchase Obligations	12 Months Ended
Unconditional Purchase Obligations	Dec. 31, 2011
Unconditional Purchase Obligations [Abstract]
Unconditional Purchase Obligations	18. 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 $5.0 million, $2.9 million, and $3.4 million related to unconditional purchase obligations that existed as of the beginning of each year for the years ended December 31, 2011, 2010 and 2009, respectively. Future expenditures under these obligations in effect at December 31, 2011 are $4.0 million in 2012, $1.6 million in 2013 and $176,000 in 2014.

Contingencies And Commitments	12 Months Ended
Contingencies And Commitments	Dec. 31, 2011
Contingencies And Commitments [Abstract]
Contingencies And Commitments	19. Contingencies and Commitments The Company is subject to various investigations, claims and legal proceedings that arise in the ordinary course of business, including alleged infringement of intellectual property rights, commercial disputes, labor and employment matters, tax audits 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. 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, 2011. 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.

Restructuring Charges: Workforce Reduction Activities	12 Months Ended
Restructuring Charges: Workforce Reduction Activities	Dec. 31, 2011
Restructuring Charges: Workforce Reduction Activities [Abstract]
Restructuring Charges: Workforce Reduction Activities	20. Restructuring Charges: Workforce Reduction Activities On May 7, 2009, the Company announced actions it had taken or would be taking as part of an ongoing effort to manage expenses and cost structure. These actions included a reduction of approximately 6% of the Company's global workforce. During the year ended December 31, 2009, the planned restructuring activities were completed and the Company recorded related restructuring charges of approximately $3.7 million.

Subsidiary Merger Activities	12 Months Ended
Subsidiary Merger Activities	Dec. 31, 2011
Subsidiary Merger Activities [Abstract]
Subsidiary Merger Activities	21. Subsidiary Merger Activities To improve the effectiveness of the Company's operations in Japan, the Company completed the merger of its Japan subsidiaries during the third quarter of 2010. For tax purposes in Japan, this transaction resulted in a step-up in the tax basis of certain assets and liabilities of the merged subsidiary to fair value as of the date of the merger and gave rise to a taxable gain in Japan, resulting in a liability of approximately $77.3 million which was paid during the fourth quarter of 2010. The unamortized portion of the corresponding prepaid tax, which is deductible over the succeeding five-year period in Japan for the stepped-up tax basis of the assets and liabilities, is included on the consolidated balance sheets as of December 31, 2011 and 2010. For U.S. tax purposes, this taxable gain in Japan gave rise to a foreign tax credit that reduced the current U.S. tax on foreign income. The Company's U.S. tax payments were reduced by approximately $22.2 million in 2010 as a result of this credit. The Company recently filed an amended tax return in order to request a refund of approximately $26.3 million for a portion of this foreign tax credit which can be carried back to reduce the tax obligation of previous years. The remaining portion of this foreign tax credit (approximately $0.2 million) will be used to reduce the amount of taxes to be paid in future periods. Recognition of this foreign tax credit will be recognized as a reduction to the Company's U.S. taxes over the same five-year period that the prepaid tax in Japan is recognized.

Organization (Details)	12 Months Ended
Organization (Details)	Dec. 31, 2011
Organization [Abstract]
Number of operating segments of Ansys	2

Summary Of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2011 USD ($) years months	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives, minimum (years) \| years	1
Property and equipment, estimated useful lives, maximum (years) \| years	40
Amortization expense related to software costs	$ 33,728,000	$ 32,757,000	$ 36,011,000
Cash, uninsured amount	297,700,000
Provisions for doubtful accounts	404,000	1,757,000	1,610,000
Net foreign exchange losses	$ 430,000	400,000	1,400,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Frequency period of major product upgrades (months) \| months	12
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Frequency period of major product upgrades (months) \| months	18
Credit Concentration Risk [Member]
Summary Of Significant Accounting Policies [Line Items]
Uninsured cash balances held outside U.S.	$ 153,400,000
Cash equivalent balances with U.S. financial institution	227,500,000
FDIC [Member] \| Credit Concentration Risk [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash accounts held in U.S. banks	250,000
SIPC [Member] \| Credit Concentration Risk [Member]
Summary Of Significant Accounting Policies [Line Items]
SIPC insurance limit per customer	$ 500,000
Acquired And Internally Developed Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated life of capitalized software products, (years) \| years	3
Amortization expense related to software costs	$ 33,700,000	$ 32,800,000	$ 36,000,000

Summary Of Significant Accounting Policies (Summary Of Cash And Cash Equivalents) (Details) - USD ($) $ in Thousands	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Summary Of Significant Accounting Policies [Abstract]
Cash accounts	$ 289,298	$ 170,765
Money market mutual funds	181,198	273,926
Time deposits	1,332	27,788
Total	$ 471,828	$ 472,479	$ 335,878	$ 228,176
Money market mutual funds, % of Total	38.40%	58.00%
Time deposits, % of Total	0.30%	5.90%
Cash accounts, % of Total	61.30%	36.10%

Acquisitions (Narrative) (Details) $ in Thousands	5 Months Ended	7 Months Ended	12 Months Ended
Acquisitions (Narrative) (Details) $ in Thousands	Dec. 31, 2011 USD ($)	Aug. 01, 2011 USD ($) years	Dec. 31, 2011 USD ($)
Business Acquisition [Line Items]
Business combination, goodwill recognized, description			<font style="font-family: Times New Roman;" class="_mt" size="2">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 Apache.</font>
Business acquisition, incentive and provision fiscal period (in years) \| years		3
Acquisition-related costs			$ 2,100
Increase in of identifiable intangible assets during measurement period			2,300
Reduction in values of net deferred tax liabilities during measurement period			1,900
Reduction in values of goodwill during measurement period			$ 4,300
Nature of preliminary adjustments			These adjustments were based on refinements to assumptions used in the preliminary valuation of intangible assets and new information obtained in the calculation of the net deferred tax liabilities.
Apache Design Solutions, Inc. [Member]
Business Acquisition [Line Items]
Business acquisition, acquisition percentage		100.00%
Business acquisition, purchase price		$ 313,977
Business acquisition, cash on subsidiary balance sheet	$ 31,948		$ 31,948
ANSYS replacement stock options		3,170
Contingent consideration	9,600	(9,501)	9,600
Business acquisition, potential performance equity awards	13,000		13,000
Revenues of acquired business	14,500
Net loss from acquired business	4,200
Contingent consideration arrangement, additional payments		$ 12,000
Acquired deferred revenue	10,100		10,100
Acquired deferred revenue, amount lower than the historical carrying value recorded on the opening balance sheet	$ 13,600		13,600
Acquired deferred revenue, impact on reported revenue			9,600
Acquired deferred revenue, expected impact on reported revenue in next fiscal year			$ 3,400

Acquisitions (Fair Value Of Consideration Transferred) (Details) - Apache Design Solutions, Inc. [Member] - USD ($) $ in Thousands	Dec. 31, 2011	Aug. 01, 2011
Business Acquisition [Line Items]
Cash		$ 301,306
Contingent consideration	$ (9,600)	9,501
ANSYS replacement stock options		3,170
Total consideration transferred at fair value		$ 313,977

Acquisitions (Recognized Amounts Of Identifiable Assets Acquired And Liabilities) (Details) - Apache Design Solutions, Inc. [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2011 USD ($) years
Business Acquisition [Line Items]
Cash and short term investments	$ 31,948
Accounts receivable and other tangible assets	6,011
Accounts payable and other liabilities	(16,646)
Deferred revenue	(10,100)
Net deferred tax liabilities	(44,283)
Total identifiable net assets	123,030
Goodwill	190,947
Developed Software [Member]
Business Acquisition [Line Items]
Amortizable intangible assets	$ 82,500
Useful life of intangible assets acquired, in years \| years	7
Customer Relationships [Member]
Business Acquisition [Line Items]
Amortizable intangible assets	$ 36,100
Useful life of intangible assets acquired, in years \| years	15
Contract Backlog [Member]
Business Acquisition [Line Items]
Amortizable intangible assets	$ 13,500
Useful life of intangible assets acquired, in years \| years	3
Platform Trade names [Member]
Business Acquisition [Line Items]
Indefinite-lived intangible assets	$ 21,900
Apache Trade Name [Member]
Business Acquisition [Line Items]
Amortizable intangible assets	$ 2,100
Useful life of intangible assets acquired, in years \| years	6

Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2011	Dec. 31, 2010
Components for Other Receivables and Current Assets [Line Items]
Other receivables and current assets	$ 163,296	$ 147,402
Accounts Receivable Portion Of Annual Lease Licenses And Software Maintenance [Member]
Components for Other Receivables and Current Assets [Line Items]
Other receivables and current assets	112,800	89,900
Taxes Receivable Related To Overpayments And Refunds [Member]
Components for Other Receivables and Current Assets [Line Items]
Other receivables and current assets	$ 36,000	$ 32,900

Property And Equipment (Components Of Property And Equipment) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2011 USD ($) years	Dec. 31, 2010 USD ($)
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 106,549	$ 90,326
Less: Accumulated depreciation and amortization	(60,911)	(53,405)
Property and equipment, net	$ 45,638	36,921
Property and equipment, Estimated Useful Lives, minimum \| years	1
Property and equipment, Estimated Useful Lives, maximum \| years	40
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 55,221	41,998
Property and equipment, Estimated Useful Lives, minimum	1
Property and equipment, Estimated Useful Lives, maximum	10
Computer Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 26,709	25,896
Property and equipment, Estimated Useful Lives, minimum	1
Property and equipment, Estimated Useful Lives, maximum	5
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 10,469	9,921
Property and equipment, Estimated Useful Lives, minimum	10
Property and equipment, Estimated Useful Lives, maximum	40
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 7,394	6,566
Property and equipment, Estimated Useful Lives, minimum	1
Property and equipment, Estimated Useful Lives, maximum	10
Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 5,007	4,577
Property and equipment, Estimated Useful Lives, minimum	1
Property and equipment, Estimated Useful Lives, maximum	13
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,749	$ 1,368

Goodwill And Other Intangible Assets (Estimated Future Amortization Expense For Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Goodwill And Other Intangible Assets [Abstract]
Fiscal 2012	$ 66,884
Fiscal 2013	58,481
Fiscal 2014	51,889
Fiscal 2015	47,866
Fiscal 2016	40,280
Thereafter	95,763
Total intangible assets subject to amortization	361,163
Indefinite-lived trademarks	22,257
Other intangible assets, net	$ 383,420	$ 278,320

Long-Term Debt (Schedule Of Borrowings) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Long-Term Debt [Abstract]
Term loan payable in quarterly installments with a final maturity of July 31, 2013	$ 127,557	$ 159,446
Capitalized lease obligations	15	79
Total	127,572	159,525
Less current portion	(74,423)	(31,962)
Long-term debt and capital lease obligations, net of current portion	$ 53,149	$ 127,563
Long-term debt maturity date	Jul. 31, 2013

Long-Term Debt (Future Principal Payments On Company's Term Loan) (Details) - USD ($) $ in Thousands	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Term loan balance payable as of December 31, 2011	$ 127,557	$ 159,446
March 31, 2012 [Member]
Debt Instrument [Line Items]
Future principal payments on company's term loan, 2012	10,630
June 30, 2012 [Member]
Debt Instrument [Line Items]
Future principal payments on company's term loan, 2012	10,630
September 30, 2012 [Member]
Debt Instrument [Line Items]
Future principal payments on company's term loan, 2012	26,574
December 31, 2012 [Member]
Debt Instrument [Line Items]
Future principal payments on company's term loan, 2012	26,574
March 31, 2013 [Member]
Debt Instrument [Line Items]
Future principal payments on company's term loan, 2013	26,574
July 31, 2013 (Maturity) [Member]
Debt Instrument [Line Items]
Future principal payments on company's term loan, 2013	$ 26,575

Fair Value Measurement (Narrative) (Details)	12 Months Ended
Fair Value Measurement (Narrative) (Details)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Aug. 01, 2011 USD ($)
Fair Value Measurement [Line Items]
Unrealized gains or losses associated with deposits	$ 0	$ 0
Short-term investment time deposits maturity minimum, in months	3
Short-term investment time deposits maturity maximum, in years	1
Transfer amounts in or out of Level 1 or Level 2 fair value measurements	$ 0
Deferred compensation	2,073,000
Apache Design Solutions, Inc. [Member]
Fair Value Measurement [Line Items]
Contingent consideration arrangement, additional payments			$ 12,000,000
Contingent consideration	$ 9,600,000		$ (9,501,000)

Fair Value Measurement (Assets And Liabilities Carried At Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 182,530	$ 301,714
Short-term investments	576	455
Deferred compensation	(2,073)
Contingent consideration	(9,571)
Quoted Prices In Active Markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	181,198	273,926
Short-term investments	0	0
Deferred compensation	0
Contingent consideration	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1,332	27,788
Short-term investments	576	455
Deferred compensation	0
Contingent consideration	0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Short-term investments	0	$ 0
Deferred compensation	(2,073)
Contingent consideration	$ (9,571)

Fair Value Measurement (Fair Value Liabilities Measured Using Significant Unobservable Inputs) (Details) - Significant Unobservable Inputs (Level 3) [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2011 USD ($)
Deferred Compensation [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance-January 1, 2011	$ 0
Issuances	2,057
Interest expense included in earnings	16
Ending balance-December 31, 2011	2,073
Contingent Consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance-January 1, 2011	0
Issuances	9,501
Interest expense included in earnings	70
Ending balance-December 31, 2011	$ 9,571

Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
Income Taxes (Narrative) (Details) - USD ($)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Aug. 01, 2011
Income Tax Contingency [Line Items]
Tax credit carryforwards	$ 12,800,000
Total unrecognized tax benefit that would not affect the effective tax rate, if recognized	5,800,000
Liability for penalties	2,200,000	$ 455,000
Liability for interest	$ 2,600,000	2,000,000
Years open to examination	2007 through 2010
Years under examination	2007
Foreign deferred tax expense	$ 10,061,000	$ (9,366,000)	$ (7,474,000)
Effective tax rate	31.80%	29.20%	32.90%
Subject To Utilization Limitations [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	$ 8,000,000
Not Subject To Expiration [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	1,300,000
Subject To Expiration [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards	$ 11,500,000
Tax credit carryforwards, expiration period	between 2012 and 2031
Investments In Foreign Subsidiaries And Foreign Corporate Joint Ventures That Are Essentially Permanent In Duration [Member]
Income Tax Contingency [Line Items]
Amount in excess of the amount for financial reporting over the tax bases	$ 137,700,000
Assumed In Business Combination [Member]
Income Tax Contingency [Line Items]
Liability for penalties				$ 2,100,000
Liability for interest				$ 546,000
Federal Domestic [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 3,200,000
Net operating loss carryforwards, expiration period	2028
Foreign Country [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 48,300,000
State And Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 9,500,000
Net operating loss carryforwards, expiration period	between 2016 and 2030
Effective Income Tax Rate Excluding Japan Rate Change [Member]
Income Tax Contingency [Line Items]
Effective tax rate	30.00%
Japanese Corporate Tax Rate Change Impact [Member]
Income Tax Contingency [Line Items]
Foreign deferred tax expense	$ 4,800,000
Operating Loss Carryforward With No Expiration Date [Member] \| Foreign Country [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	6,600,000
Operating Loss Carryforward Expiring Between 2019-2026 [Member] \| Foreign Country [Member] \| Subject To Expiration [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 41,700,000
Net operating loss carryforwards, expiration period	between 2019 and 2026
Subject To Utilization Limitations [Member] \| State And Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 7,400,000

Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2011	Dec. 31, 2010
Income Taxes [Abstract]
Net operating loss carryforwards	$ 18,624	$ 12,402
Employee benefits	16,697	14,788
Stock-based compensation	11,888	8,916
Foreign tax credits	7,219	4,398
Other accruals not currently deductible	6,090	8,386
Research and development credits	4,542	1,429
Uncertain tax positions	3,145	3,084
Deferred revenue	3,096	5,089
Allowance for doubtful accounts	1,259	1,587
Investments	0	229
Other	1,241	588
Valuation allowance	(8)	(977)
Deferred tax assets	73,793	59,919
Other intangible assets	(141,949)	(108,071)
Property and equipment	(6,529)	(3,430)
Unremitted foreign earnings	(140)	(171)
Deferred tax liabilities	(148,618)	(111,672)
Net deferred tax liabilities	$ (74,825)	$ (51,753)

Non-Compete And Employment Agreements (Details)	12 Months Ended
Non-Compete And Employment Agreements (Details)	Dec. 31, 2011 USD ($)
Board Of Directors Chairman [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected severance costs in the event of termination of chairman	$ 300,000

Stock Option And Grant Plan (Narrative) (Details)	3 Months Ended		6 Months Ended	12 Months Ended			24 Months Ended
Stock Option And Grant Plan (Narrative) (Details)	Mar. 31, 2011 shares	Mar. 31, 2010 shares	Jun. 30, 2011 shares	Dec. 31, 2011 USD ($) years $ / shares shares	Dec. 31, 2010 USD ($) $ / shares	Dec. 31, 2009 USD ($)	Dec. 31, 2011 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for grant under the plan \| shares				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 \| years				10
Expiration period for optionee who meets the 10% criteria \| years				5
Duration of offering the purchase plan				4 years
Maximum months after sale event where awards fully vest when service relationship terminated without cause				18
Maximum number of days that may be granted to terminated employee to exercise awards prior to termination				15
Total estimated grant date fair values of stock options vested during period				$ 20,200,000	$ 16,700,000	$ 12,400,000
Total unrecognized estimated compensation cost				$ 58,800,000			$ 58,800,000
Weighted average period of recognition of unrecognized compensation cost (years) \| years				2.0
Total intrinsic value of options exercised during the period				$ 42,600,000	88,000,000	82,900,000
Unvested options \| shares				3,300,000			3,300,000
Aggregate intrinsic value of unvested options				$ 44,300,000			$ 44,300,000
Weighted average exercise price of unvested options \| $ / shares				$ 44.28			$ 44.28
Weighted average remaining contractual term of unvested stock options (years) \| years				8.50
Cash received from the exercise of stock options				$ 22,791,000	22,929,000	15,361,000
Tax benefit from exercise of stock options				12,400,000
Excess tax benefit from exercise of stock options				$ 10,046,000	$ 11,753,000	$ 13,168,000
Deferred Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred stock units earned with underlying shares remaining unissued until the service termination \| shares			13,631	66,704			66,704
Deferred stock units earned during the period \| shares			2,031	21,684
Performance-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance-based restricted stock units granted \| shares	92,500	80,500
Measurement period of restricted stock units				3 years
Value of the restricted stock units on the grant date \| $ / shares				$ 32.05	$ 25.00		$ 32.05
Total compensation expense recorded under the Purchase Plan				$ 1,600,000	$ 590,000		$ 5,000,000
Compensation expense expected to be recorded in 2012				1,800,000
Compensation expense expected to be recorded in 2013				$ 1,000,000

Stock Option And Grant Plan (Summary Of Stock Options) (Details) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2011 USD ($) $ / shares years shares	Dec. 31, 2010 USD ($) $ / shares years shares	Dec. 31, 2009 USD ($) $ / shares years shares
Stock Option And Grant Plan [Abstract]
Outstanding, beginning of year, Options \| shares	7,319	8,110	9,216
Granted, Options \| shares	1,104	1,204	1,317
Issued pursuant to apache Acquisition, Options \| shares	418	0	0
Exercised, Options \| shares	(1,179)	(1,924)	(2,299)
Forfeited, Options \| shares	(117)	(71)	(124)
Outstanding, end of year, Options \| shares	7,545	7,319	8,110
Vested and Exercisable, end of year, Options \| shares	4,251	4,214	4,914
Outstanding, beginning of period, Weighted Average Exercise Price \| $ / shares	$ 29.92	$ 22.94	$ 16.91
Granted, Weighted Average Exercise Price \| $ / shares	$ 58.50	$ 48.35	$ 37.13
Issued pursuant to Apache acquisition, Weighted Average Exercise Price \| $ / shares	18.66	0.00	0.00
Exercised, Weighted Average Exercise Price \| $ / shares	$ 19.33	$ 11.92	$ 6.68
Forfeited, Weighted Average Exercise Price \| $ / shares	33.27	32.40	27.08
Outstanding, end of period, Weighted Average Exercise Price \| $ / shares	35.10	29.92	22.94
Vested and Exercisable, end of period, Weighted Average Exercise Price \| $ / shares	$ 27.98	$ 23.11	$ 16.74
Outstanding, Weighted Average Remaining Contractual Term (in years) \| years	6.66	6.54	6.16
Vested and Exercisable, Weighted Average Remaining Contractual Term (in years) \| years	5.20	5.16	4.72
Outstanding, Aggregate Intrinsic Value \| $	$ 168,837	$ 162,099	$ 166,531
Vested and Exercisable, Aggregate Intrinsic Value \| $	$ 124,550	$ 122,022	$ 131,334