ANSYS (ANSS) 10-K 22 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 16, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	ANSS
Entity Registrant Name	ANSYS INC
Entity Central Index Key	1,013,462
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		83,871,362
Entity Well-Known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 7,251,000,000

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 881,501	$ 822,479
Short-term investments	286	381
Accounts receivable, less allowance for doubtful accounts of $6,800 and $5,700, respectively	124,659	107,192
Other receivables and current assets	263,820	239,349
Total current assets	1,270,266	1,169,401
Property and equipment, net	57,096	54,677
Goodwill	1,378,553	1,337,215
Other intangible assets, net	157,625	172,619
Other long-term assets	35,972	24,287
Deferred income taxes	42,111	42,327
Total assets	2,941,623	2,800,526
Current liabilities:
Accounts payable	6,042	7,395
Accrued bonuses and commissions	69,925	49,487
Accrued income taxes	5,760	5,263
Other accrued expenses and liabilities	86,335	73,676
Deferred revenue	440,491	403,279
Total current liabilities	608,553	539,100
Long-term liabilities:
Deferred income taxes	1,461	2,259
Other long-term liabilities	85,778	50,762
Total long-term liabilities	87,239	53,021
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	873,357	883,010
Retained earnings	2,316,916	2,057,665
Treasury stock, at cost: 9,044,498 and 7,548,188 shares, respectively	(907,530)	(675,550)
Accumulated other comprehensive loss	(37,844)	(57,652)
Total stockholders’ equity	2,245,831	2,208,405
Total liabilities and stockholders’ equity	$ 2,941,623	$ 2,800,526

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Software licenses	$ 624,964	$ 568,174	$ 555,105
Maintenance and service	470,286	420,291	387,648
Total revenue	1,095,250	988,465	942,753
Cost of sales:
Software licenses	34,421	28,860	29,105
Amortization	36,794	38,092	38,755
Maintenance and service	78,949	79,908	79,386
Total cost of sales	150,164	146,860	147,246
Gross profit	945,086	841,605	795,507
Operating expenses:
Selling, general and administrative	338,640	269,515	253,603
Research and development	202,746	183,093	168,831
Amortization	12,972	12,755	19,394
Total operating expenses	554,358	465,363	441,828
Operating income	390,728	376,242	353,679
Interest income	6,962	4,209	2,829
Other (expense) income, net	(1,996)	(136)	257
Income before income tax provision	395,694	380,315	356,765
Income tax provision	136,443	114,679	104,244
Net income	$ 259,251	$ 265,636	$ 252,521
Earnings per share – basic:
Earnings per share	$ 3.05	$ 3.05	$ 2.82
Weighted average shares	84,988	87,227	89,561
Earnings per share – diluted:
Earnings per share	$ 2.98	$ 2.99	$ 2.76
Weighted average shares	86,854	88,969	91,502

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 6,800	$ 5,700
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	93,236,023	93,236,023
Treasury stock, shares	9,044,498	7,548,188

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 259,251	$ 265,636	$ 252,521
Other comprehensive income (loss):
Foreign currency translation adjustments	19,808	(5,488)	(20,410)
Comprehensive income	$ 279,059	$ 260,148	$ 232,111

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 259,251	$ 265,636	$ 252,521
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	67,678	69,587	77,670
Deferred income tax benefit	(2,693)	(10,921)	(15,196)
Provision for bad debts	1,474	2,009	1,304
Stock-based compensation expense	53,154	33,347	33,951
Other	21	1,290	1,413
Changes in operating assets and liabilities:
Accounts receivable	(14,406)	(17,388)	6,044
Other receivables and current assets	(18,498)	(39,644)	(17,662)
Other long-term assets	2,343	(7,167)	273
Accounts payable, accrued expenses and current liabilities	27,045	16,919	(6,993)
Accrued income taxes	1,215	9,052	5,770
Deferred revenue	20,648	41,430	40,566
Other long-term liabilities	33,206	1,830	(3,962)
Net cash provided by operating activities	430,438	365,980	375,699
Cash flows from investing activities:
Acquisitions, net of cash acquired	(63,885)	(7,891)	(46,117)
Capital expenditures	(19,149)	(12,443)	(16,145)
Other investing activities	(14,409)	(11,839)	230
Net cash used in investing activities	(97,443)	(32,173)	(62,032)
Cash flows from financing activities:
Purchase of treasury stock	(336,042)	(336,335)	(337,910)
Restricted stock withholding taxes paid in lieu of issued shares	(11,112)	(5,057)	(4,446)
Contingent consideration payments	0	(1,048)	(1,173)
Proceeds from shares issued for stock-based compensation	52,503	53,811	43,623
Other financing activities	0	(1)	(21)
Net cash used in financing activities	(294,651)	(288,630)	(299,927)
Effect of exchange rate fluctuations on cash and cash equivalents	20,678	(6,866)	(17,636)
Net increase (decrease) in cash and cash equivalents	59,022	38,311	(3,896)
Cash and cash equivalents, beginning of period	822,479	784,168	788,064
Cash and cash equivalents, end of period	881,501	822,479	784,168
Supplemental disclosures of cash flow information:
Income taxes paid	116,389	118,455	107,218
Interest paid	199	822	620
Fair value of stock options and restricted stock awards assumed in connection with acquisitions	$ 0	$ 0	$ 3,528

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive (Loss)/Income
Beginning balance at Dec. 31, 2014	$ 2,217,501	$ 932	$ 904,825	$ 1,539,508	$ (196,010)	$ (31,754)
Beginning 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)/income	(20,410)					(20,410)
Net income for the year	252,521			252,521
Acquisition-related activity	3,528		(1,922)		$ 5,450
Stockholders' Equity, Other 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
Treasury shares acquired	$ (336,335)				$ (336,335)
Treasury shares acquired, shares	3,700				3,700
Stock-based compensation activity, including tax benefit	$ 90,165		(11,459)		$ 101,624
Stock-based compensation activity, including tax benefit, shares					(1,249)
Other comprehensive (loss)/income	(5,488)					(5,488)
Net income for the year	265,636			265,636
Ending balance at Dec. 31, 2016	2,208,405	$ 932	883,010	2,057,665	$ (675,550)	(57,652)
Ending balance, shares at Dec. 31, 2016		93,236			7,548
Treasury shares acquired	$ (336,042)				$ (336,042)
Treasury shares acquired, shares	2,750				2,750
Stock-based compensation activity, including tax benefit	$ 94,409		(9,653)		$ 104,062
Stock-based compensation activity, including tax benefit, shares					(1,254)
Other comprehensive (loss)/income	19,808					19,808
Net income for the year	259,251
Ending balance at Dec. 31, 2017	$ 2,245,831	$ 932	$ 873,357	$ 2,316,916	$ (907,530)	$ (37,844)
Ending balance, shares at Dec. 31, 2017		93,236			9,044

CONSOLIDATED STATEMENTS OF STO8

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (PARENTHETICAL) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Stock-based compensation activity, tax benefit	$ 0	$ 8,065	$ 6,068

Organization

Organization	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization ANSYS, Inc. (hereafter the Company or ANSYS) develops and globally markets engineering simulation software and services widely used by engineers, designers, researchers and students across a broad spectrum of industries and academia, including aerospace and defense, automotive, electronics, semiconductors, energy, materials and chemical processing, turbomachinery, consumer products, healthcare, and sports. As defined by the accounting guidance for segment reporting, the Company operates as one segment. Given the integrated approach to the multi-discipline problem-solving needs of the Company's customers, a single sale of software may contain components from multiple product areas and include combined technologies. The Company also has a multi-year product and integration strategy that will result in new, combined products or changes to the historical product offerings. As a result, it is impracticable for the Company to provide accurate historical or current reporting among its various product lines.

Accounting Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Accounting Policies	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, including those related to the Tax Cuts and Jobs Act • Uncertain tax positions • Tax valuation reserves • Fair value of stock-based compensation and probabilities of performance award attainment • Contract revenue • Acquired deferred revenue • Useful lives for depreciation and amortization • Valuations of goodwill and other intangible assets • Deferred compensation • Loss contingencies Actual results could differ from these estimates. Changes in estimates are recorded in the results of operations in the period that the changes occur. Revenue Recognition Revenue 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. The Company includes the revenue for the entire lease 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 funds. Cash equivalents are carried at cost, which approximates fair value. The Company's cash and cash equivalents balances comprise the following: December 31, 2017 December 31, 2016 (in thousands, except percentages) Amount % of Total Amount % of Total Cash accounts $ 568,587 64.5 $ 488,504 59.4 Money market funds 312,914 35.5 333,975 40.6 Total $ 881,501 $ 822,479 The Company's money market fund balances are held in various funds of a single issuer. Property and Equipment Property and equipment is stated at cost. Depreciation is computed using the straight-line method over the estimated useful lives of the various classes of assets, which range from one to forty years. Repairs and maintenance are charged to expense as incurred. Gains or losses from the sale or retirement of property and equipment are included in operating income. Research and Development Research and development costs, other than certain capitalized software development costs, are expensed as incurred. 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 and acquired software and technology. Intangible assets that are not considered to have an indefinite useful life are amortized over their useful lives, which are generally two to fifteen years. Amortization expense for intangible assets was $49.8 million , $50.8 million and $58.1 million for the years ended December 31, 2017 , 2016 and 2015 , 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 as of January 1 of each year unless there is an indicator that would require a test during the year. The Company periodically reviews the carrying value of other intangible assets and will recognize impairments when events or circumstances indicate that such assets may be impaired. Concentrations of Credit Risk The Company has a concentration of credit risk with respect to revenue and trade receivables due to the use of certain significant channel partners to market and sell the Company's products. The Company performs periodic credit evaluations of its customers' financial condition and generally does not require collateral. The following table outlines concentrations of risk with respect to the Company's revenue: Year Ended December 31, (as a % of revenue) 2017 2016 2015 Revenue from channel partners 25 % 24 % 24 % Largest channel partner 5 % 5 % 5 % 2 nd largest channel partner 2 % 2 % 2 % No single customer accounted for more than 5% of the Company's revenue in 2017 , 2016 or 2015 . 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) 2017 2016 Cash and cash equivalents held domestically $ 561,417 $ 593,348 Cash and cash equivalents held by foreign subsidiaries 320,084 229,131 Cash and cash equivalents held in excess of deposit insurance, foreign and domestic 852,138 805,374 Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic 328,902 377,602 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 $1.5 million , $2.0 million and $1.3 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period of the enactment date. The Company records net deferred tax assets to the extent it believes these assets will more likely than not be realized. In making such determination, the Company considers all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax planning strategies and recent financial operations. In the event the Company determines that it will be able to realize deferred tax assets for which a valuation allowance was used to reduce their carrying value, the adjustment to the valuation allowance will be recorded as a reduction to the provision for income taxes. Tax benefits related to uncertain tax positions taken or expected to be taken on a tax return are recorded when such benefits meet a more-likely-than-not threshold. Otherwise, these tax benefits are recorded when a tax position has been effectively settled, which means that the statute of limitations has expired or the appropriate taxing authority has completed its examination even though the statute of limitations remains open. The Company recognizes interest and penalties related to income taxes within the income tax expense line in the consolidated statements of income. Accrued interest and penalties are included within the related tax liability line in the consolidated balance sheets. Foreign Currencies Certain of the Company's sales and intercompany transactions are denominated in foreign currencies. These transactions are translated to the functional currency at the exchange rate on the transaction date. Assets and liabilities denominated in a currency other than the Company's or subsidiary's functional currency are translated at the effective exchange rate on the balance sheet date. Gains and losses resulting from foreign exchange transactions are included in other (expense) income, net. The Company recorded net foreign exchange losses of $1.9 million for the year ended December 31, 2017 , and net foreign exchange gains of $0.1 million and $0.5 million for the years ended December 31, 2016 and 2015 , 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 awards are anti-dilutive, they are excluded from the calculation of diluted EPS. The details of basic and diluted EPS are as follows: Year Ended December 31, (in thousands, except per share data) 2017 2016 2015 Net income $ 259,251 $ 265,636 $ 252,521 Weighted average shares outstanding – basic 84,988 87,227 89,561 Dilutive effect of stock plans 1,866 1,742 1,941 Weighted average shares outstanding – diluted 86,854 88,969 91,502 Basic earnings per share $ 3.05 $ 3.05 $ 2.82 Diluted earnings per share $ 2.98 $ 2.99 $ 2.76 Anti-dilutive shares 84 260 206 Stock-Based Compensation The Company accounts for stock-based compensation in accordance with share-based payment accounting guidance. The guidance requires an entity to measure the cost of employee services received in exchange for an award of equity instruments based on the grant-date fair value of the award. The cost is recognized over the period during which an employee is required to provide service in exchange for the award, typically the vesting period. Fair Value of Financial Instruments The Company accounts for certain assets and liabilities at fair value in accordance with the accounting guidance applicable to fair value measurements and disclosures. The carrying values of cash, cash equivalents, short-term investments, accounts receivable, accounts payable, accrued expenses, other accrued liabilities and short-term obligations are deemed to be reasonable estimates of their fair values because of their short-term nature. New Accounting Guidance Revenue from contracts with customers: In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (ASU 2014-09). ASU 2014-09 supersedes most current revenue recognition guidance, including industry-specific guidance. Previous 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. The standard also requires disclosure of the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. 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. This standard is effective for the Company on January 1, 2018. Entities have the option of using a full retrospective, cumulative effect or modified retrospective approach to adopt ASU 2014-09. The Company will utilize the modified retrospective implementation approach. The Company expects a cumulative-effect adjustment to increase retained earnings by $230.0 million - $260.0 million , or $165.0 million - $190.0 million net of income tax, on January 1, 2018, primarily derived from revenue related to software lease licenses. This update will impact the timing and amounts of revenue recognized, which will result in increased volatility in the amount of revenue recognized each period. The Company expects that the adoption of this standard will have a material impact on the Company’s consolidated financial statements. While the Company expects that the standard will impact various elements of its business, the most significant impact is expected to be on the recognition of revenue related to software lease licenses. These licenses include the right to use the software and PCS over the term of the license. These licenses are currently recognized as lease license revenue ratably over the term of the license. Under the new standard and the existing interpretations, the Company expects to recognize approximately 50% of the revenue related to these licenses up-front at the time the license is delivered. The up-front portion will continue to be reported within lease license revenue, but the ratable portion allocation to PCS will be reflected in maintenance revenue, resulting in a significant shift from software license revenue to maintenance and services revenue as reported on the consolidated statement of income. In addition, it is anticipated that there will be an acceleration of income tax payments associated with deferred revenue and backlog credited to retained earnings and never recognized as revenue in the financial statements. The 2018 acceleration of cash payments is expected to be between $15.0 million - $20.0 million . The Company has also made a preliminary assessment that the expense related to sales commissions will not be materially different under the new standard. However, the Company's preliminary assessments could change as additional interpretations relating to the new standard are provided and as issues identified by software industry groups are addressed. Leases: In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) (ASU 2016-02). ASU 2016-02 requires virtually all leases, other than leases that meet the definition of a short-term lease or leases of intangible assets, to be recorded on the balance sheet with a right-of-use asset and corresponding lease liability. Leases will be classified as either operating or finance leases based on certain criteria. This classification will determine the timing and presentation of expenses on the income statement, as well as the presentation of related cash flows. The standard is effective for annual periods beginning after December 15, 2018, including interim periods within that reporting period. Early adoption is permitted and a modified retrospective transition is required upon adoption. The Company does not expect to early adopt and continues to evaluate the effect that this update will have on its financial results upon adoption. The Company's preliminary assessment is that this update may materially increase the Company's assets and liabilities upon adoption. The Company has completed the initial inventory of its leases and policy elections, and the Company is currently developing new processes and controls to meet the accounting and disclosure requirements under the new standard. Employee share-based payment accounting: In March 2016, the FASB issued Accounting Standards Update No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (ASU 2016-09). This update includes various areas for simplification related to aspects of the accounting for share-based payment transactions. One simplification is that the tax effects of share-based payment settlements will be recorded in the income statement. Prior guidance required tax windfalls at settlement, and tax shortfalls to the extent of previous windfalls, to be recorded in equity. This provision was required to be adopted prospectively. The Company adopted the guidance during the quarter ended March 31, 2017. The primary impact of adoption was the recognition of excess tax benefits in the Company's provision for income taxes rather than paid-in capital, which resulted in the recognition of excess tax benefits in the provision for income taxes of $13.3 million during the year ended December 31, 2017. In addition, the Company applied the change in classification of such benefits from financing to operating on the consolidated statements of cash flows on a retrospective basis, resulting in an increase to both net cash provided by operating activities and net cash used in financing activities of $9.2 million and $8.2 million for the years ended December 31, 2016 and 2015, respectively. Credit losses: In June 2016, the FASB issued Accounting Standards Update No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13). Previous guidance requires the allowance for doubtful accounts to be estimated based on an incurred loss model, which considers past and current conditions. ASU 2016-13 requires companies to use an expected loss model that also considers reasonable and supportable forecasts of future conditions. ASU 2016-13 is effective for annual periods beginning after December 15, 2019, including interim periods within that reporting period. Early adoption is permitted for annual periods beginning after December 15, 2018, including interim periods within that reporting period. The standard requires a cumulative-effect adjustment to the statement of financial position as of the beginning of the first reporting period in which the guidance is effective. The Company is currently evaluating the effect that this update will have on its financial results upon adoption. Income taxes: In October 2016, the FASB issued Accounting Standards Update No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (ASU 2016-16). Previous guidance requires the tax effects from intra-entity asset transfers to be deferred until the asset is sold to a third party or recovered through use. ASU 2016-16 eliminates this deferral for all intra-entity asset transfers other than inventory. The standard is effective for annual periods beginning after December 15, 2017, including interim periods within that reporting period. Early adoption is permitted and a modified retrospective transition is required upon adoption. The Company plans to adopt ASU 2016-16 effective January 1, 2018 and expects adoption to have an immaterial effect, if any, on its financial results. Business combinations: In January 2017, the FASB issued Accounting Standards Update No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business (ASU 2017-01). This update narrows the definition of a business. If substantially all the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets, the acquiree is not a business. The update also requires a business to include an input and a substantive process that significantly contributes to the ability to create outputs. This definition is expected to reduce the number of acquisitions accounted for as business combinations, which will impact the accounting treatment of certain items, including the accounting treatment of contingent consideration and transaction expenses. ASU 2017-01 is effective for annual periods beginning after December 15, 2017, including interim periods within that reporting period. Early adoption is permitted and the update will be applied prospectively. The effect of the implementation will depend upon the nature of the Company's future acquisitions, if any. Historically, the Company has entered into acquisitions that would meet the definition of a business under ASU 2017-01. The Company plans to adopt ASU 2017-01 effective January 1, 2018.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions	Acquisitions During the years ended December 31, 2017 , 2016 and 2015 the Company completed various acquisitions to expand its customer base and accelerate the development of new and innovative products to the marketplace while lowering design and engineering costs for customers. The acquisitions were not individually significant. The combined purchase prices of the acquisitions purchased during the years ended December 31, 2017 , 2016 and 2015 were approximately $67.0 million , $10.3 million and $49.7 million , respectively. The 2017 technology acquisitions are further described in the table below: Date of Closing Company Details November 15, 2017 3DSIM 3DSIM, a developer of premier additive manufacturing technology, gives ANSYS a complete additive manufacturing simulation workflow solution. 3DSIM's software solutions empower manufacturers, designers, materials scientists and engineers to achieve their objectives through simulation-driven innovation rather than physical trial and error. July 5, 2017 Computational Engineering International, Inc. (CEI Inc.) CEI Inc., the developer of EnSight, aids engineers and scientists in their ability to analyze, visualize and communicate large simulation data sets in clear, higher-resolution outputs. March 10, 2017 CLK Design Automation (CLK-DA) CLK-DA offers fast transistor simulation technology that complements the Company's semiconductor product portfolio. The operating results of each acquisition have been included in the Company's consolidated financial statements since each respective date of acquisition. The effects of the business combinations were not material to the Company's consolidated results of operations individually or in the aggregate. In valuing deferred revenue on the balance sheets of the Company's acquisitions as of their respective acquisition dates, the Company applied the fair value provisions applicable to the accounting for business combinations, resulting in a reduction of deferred revenue as compared to the historical carrying amounts. 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 impacts on reported revenue for the years ended December 31, 2017 , 2016 and 2015 were $2.9 million , $0.1 million and $0.8 million , respectively.

Other Receivables and Current A

Other Receivables and Current Assets	12 Months Ended
	Dec. 31, 2017
Prepaid Expense and Other Assets, Current [Abstract]
Other Receivables and Current Assets	Other Receivables and Current Assets The Company's other receivables and current assets comprise the following balances: December 31, (in thousands) 2017 2016 Receivables related to unrecognized revenue $ 215,155 $ 199,119 Income taxes receivable, including overpayments and refunds 21,663 15,718 Prepaid expenses and other current assets 27,002 24,512 Total other receivables and current assets $ 263,820 $ 239,349 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

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment consists of the following: December 31, (in thousands) Estimated Useful Lives 2017 2016 Equipment 1-10 years $ 88,189 $ 78,614 Computer software 1-5 years 34,994 30,867 Buildings and improvements 5-40 years 26,423 25,472 Leasehold improvements 1-16 years 13,316 11,571 Furniture 1-13 years 9,239 8,618 Land 1,759 1,759 Property and equipment, gross 173,920 156,901 Less: Accumulated depreciation (116,824 ) (102,224 ) Property and equipment, net $ 57,096 $ 54,677 Depreciation expense related to property and equipment was $17.9 million , $18.7 million and $19.5 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	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 2017 , the Company completed the annual impairment test for goodwill and the indefinite-lived intangible asset and determined that these assets had not been impaired as of the test date, January 1, 2017 . No other events or circumstances changed during the year ended December 31, 2017 that would indicate that the fair values of the Company's reporting unit and indefinite-lived intangible asset are below their carrying values. The Company's intangible assets and estimated useful lives are classified as follows: December 31, 2017 December 31, 2016 (in thousands) Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Finite-lived intangible assets: Developed software and core technologies (3 – 11 years) $ 365,317 $ (297,645 ) $ 338,594 $ (275,130 ) Customer lists and contract backlog (5 – 15 years) 171,048 (104,522 ) 159,549 (88,414 ) Trade names (2 – 10 years) 127,200 (104,130 ) 127,952 (90,289 ) Total $ 663,565 $ (506,297 ) $ 626,095 $ (453,833 ) Indefinite-lived intangible assets: Trade name $ 357 $ 357 Amortization expense for the intangible assets reflected above was $49.8 million , $50.8 million and $58.1 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. As of December 31, 2017 , estimated future amortization expense for the intangible assets reflected above is as follows: (in thousands) 2018 $ 39,162 2019 26,362 2020 25,449 2021 21,225 2022 16,197 Thereafter 28,873 Total intangible assets subject to amortization, net 157,268 Indefinite-lived trade name 357 Other intangible assets, net $ 157,625 The changes in goodwill during the years ended December 31, 2017 and 2016 are as follows: (in thousands) 2017 2016 Beginning balance - January 1 $ 1,337,215 $ 1,332,348 Acquisitions 36,554 6,184 Adjustments (1) (111 ) (1 ) Currency translation 4,895 (1,316 ) Ending balance - December 31 $ 1,378,553 $ 1,337,215 (1) In accordance with the accounting for business combinations, the Company recorded adjustments to goodwill for the effect of changes in the provisional fair values of the assets acquired and liabilities assumed during the measurement period (up to one year from the acquisition date) as the Company obtained new information about facts and circumstances that existed as of the acquisition date that, if known, would have affected the measurement of the amounts recognized as of that date.

Fair Value Measurement

Fair Value Measurement	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurement	Fair Value Measurement The valuation hierarchy for disclosure of assets and liabilities reported at fair value prioritizes the inputs for such valuations into three broad levels: • Level 1: quoted prices (unadjusted) in active markets for identical assets or liabilities; • Level 2: quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument; or • Level 3: unobservable inputs based on the Company's own assumptions used to measure assets and liabilities at fair value. A financial asset's or liability's classification within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement. The following tables provide the assets carried at fair value and measured on a recurring basis: Fair Value Measurements at Reporting Date Using: (in thousands) December 31, 2017 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Cash equivalents $ 312,914 $ 312,914 $ — $ — Short-term investments $ 286 $ — $ 286 $ — Deferred compensation plan investments $ 3,742 $ 3,742 $ — $ — Fair Value Measurements at Reporting Date Using: (in thousands) December 31, 2016 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Cash equivalents $ 333,975 $ 333,975 $ — $ — Short-term investments $ 381 $ — $ 381 $ — Deferred compensation plan investments $ 459 $ 459 $ — $ — The cash equivalents in the preceding tables represent money market 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 deferred compensation plan investments in the preceding tables represent trading securities held in a rabbi trust for the benefit of the non-affiliate Independent Directors. These securities consist of mutual funds traded in an active market with quoted prices. As a result, the plan assets were classified as Level 1 in the fair value hierarchy. The plan assets are recorded within other long-term assets on the Company's consolidated balance sheet. 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

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income before income taxes includes the following components: Year Ended December 31, (in thousands) 2017 2016 2015 Domestic $ 344,447 $ 340,251 $ 325,097 Foreign 51,247 40,064 31,668 Total $ 395,694 $ 380,315 $ 356,765 The provision for income taxes is composed of the following: Year Ended December 31, (in thousands) 2017 2016 2015 Current: Federal $ 112,414 $ 99,783 $ 93,853 State 7,879 8,338 7,733 Foreign 18,843 17,479 17,854 Deferred: Federal (7,387 ) (13,368 ) (14,472 ) State (584 ) (1,036 ) (1,987 ) Foreign 5,278 3,483 1,263 Total $ 136,443 $ 114,679 $ 104,244 The reconciliation of the U.S. federal statutory tax rate to the consolidated effective tax rate is as follows: Year Ended December 31, 2017 2016 2015 Federal statutory tax rate 35.0 % 35.0 % 35.0 % U.S. tax reform 4.5 — — State income taxes, net of federal benefit 1.1 1.6 1.1 Uncertain tax positions 0.3 (0.2 ) (0.4 ) Benefit from restructuring activities — (2.2 ) (2.7 ) Research and development credits (1.4 ) (1.0 ) (1.1 ) Domestic production activity benefit (2.6 ) (3.7 ) (3.1 ) Stock-based compensation (3.1 ) 0.2 — Other 0.7 0.5 0.4 34.5 % 30.2 % 29.2 % On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (Tax Reform). Tax Reform makes broad and complex changes to the U.S. tax code, including, but not limited to, (1) reducing the U.S. federal corporate tax rate from 35 percent to 21 percent ; (2) requiring companies to pay a one-time transition tax on certain unrepatriated earnings of foreign subsidiaries (Transition Tax); (3) generally eliminating U.S. federal income taxes on dividends from foreign subsidiaries; (4) creating a new provision designed to tax global intangible low-taxed income (GILTI) which allows for the possibility of using foreign tax credits (FTCs) and a deduction of up to 50 percent to offset the income tax liability (subject to some limitations); (5) repealing the domestic production activity deduction; (6) creating the base erosion anti-abuse tax, a new minimum tax; (7) allowing for full expensing of qualified property through bonus depreciation; and (8) creating limitations on the deductibility of certain executive compensation. The SEC staff issued Staff Accounting Bulletin (SAB) 118, which provides guidance on accounting for the tax effects of Tax Reform. SAB 118 provides a measurement period that should not extend beyond one year from enactment for companies to complete the accounting under ASC 740, Income Taxes . In accordance with SAB 118, a company must reflect the income tax effects of those aspects of Tax Reform for which the accounting under ASC 740 is complete in the financial statements. To the extent that a company’s accounting for certain income tax effects of Tax Reform is incomplete, but a reasonable estimate is able to be made, the company must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the tax laws that were in effect immediately before the enactment of Tax Reform. In connection with the Company’s initial analysis of the impact of Tax Reform, a discrete net tax expense of $17.9 million was recorded in the period ending December 31, 2017, primarily consisting of $1.9 million for the revaluation of net deferred tax assets and $16.0 million for the Transition Tax. As further discussed below, the Company was able to complete final or provisional calculations for certain elements of Tax Reform and the amounts and estimates are included in the financial statements. For other elements, the Company was not able to make reasonable estimates and therefore those elements have not been recorded and are accounted for in accordance with ASC 740 on the basis of the tax laws in effect before Tax Reform. The Company’s accounting for the impact of the reduction in the U.S. federal corporate tax rate on the Company's deferred tax assets and liabilities is complete. Tax Reform reduces the corporate tax rate to 21 percent , effective January 1, 2018. Consequently, the Company has recorded a net adjustment to deferred income tax expense of $1.9 million for the year ended December 31, 2017 to revalue the Company’s deferred tax assets and liabilities. The Company’s accounting for the Transition Tax is incomplete. However, reasonable estimates of certain effects were able to be calculated and, therefore, a provisional adjustment was recorded. The Transition Tax is a tax on the deemed repatriation of previously untaxed accumulated current earnings and profits (E&P) of certain foreign subsidiaries. To determine the amount of the Transition Tax, the Company must determine, in addition to other factors, the amount of post-1986 E&P of the relevant subsidiaries, as well as the amount of non-U.S. income taxes paid on such earnings. The Company was able to make a reasonable estimate of the Transition Tax and recorded a provisional Transition Tax expense of $16.0 million . However, the Company will continue to gather additional information to more precisely compute the final amount. The Company plans to elect to pay this liability over eight years and has recorded $14.5 million of the obligation in other long-term liabilities, with the balance recorded to accrued income taxes. The Company’s accounting for the indefinite reinvestment assertion is incomplete. However, a reasonable estimate of book and tax basis was calculated, and the Company made a provisional assertion. 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. As part of Tax Reform, the Company incurred U.S. tax on substantially all of the earnings of its non-U.S. subsidiaries as part of the Transition Tax. This tax increased the Company’s previously taxed earnings and will allow for the repatriation of the majority of its foreign earnings without any residual U.S. federal tax. The Company does not believe that there is an excess of the financial reporting basis over the tax basis of investments in foreign subsidiaries. Accordingly, any repatriation in excess of previously taxed earnings will be a non-taxable return of basis. This assertion is subject to change as additional information is gathered to precisely compute the book and tax basis of the Company’s non-U.S. subsidiaries. The Company’s accounting for GILTI is incomplete, and reasonable estimates of the effects are not able to be made. Therefore, no provisional adjustments were recorded. Tax Reform creates a new requirement that GILTI earned by controlled foreign corporations (CFCs) must be included currently in the gross income of the CFCs’ U.S. shareholder. GILTI is the excess of the shareholder’s “net CFC tested income” over the net deemed tangible income return which is currently defined as the excess of (1) 10 percent of the aggregate of the U.S. shareholder’s pro rata share of the qualified business asset investment of each CFC over (2) the amount of certain interest expense taken into account in the determination of net CFC-tested income. Due to the complexity of the new GILTI tax rules, the Company is continuing to evaluate this provision of Tax Reform and the application of ASC 740. Under U.S. GAAP, the Company is allowed to make an accounting policy choice of either (1) treating taxes due on future U.S. inclusions in taxable income related to GILTI as a current-period expense when incurred (the “period cost method”) or (2) factoring such amounts into the Company’s measurement of its deferred taxes (the “deferred method”). The Company’s selection of an accounting policy with respect to the new GILTI tax rules will depend, in part, on analyzing global income to determine whether future U.S. inclusions in taxable income related to GILTI are expected and, if so, the expected impact. Whether the Company expects to have future U.S. inclusions in taxable income related to GILTI depends not only on the current structure and estimated future results of global operations, but also on the Company’s intent and ability to modify the structure and/or the business. The Company is not yet able to reasonably estimate the effect of this provision of Tax Reform and therefore has not made any adjustments related to potential GILTI tax in the financial statements. In addition, the Company has not made the accounting policy decision regarding whether to record deferred taxes on GILTI or expense taxes as incurred on GILTI. The components of deferred tax assets and liabilities are as follows: December 31, (in thousands) 2017 2016 Deferred tax assets: Net operating loss carryforwards $ 21,391 $ 32,969 Stock-based compensation 17,825 23,652 Uncertain tax positions 15,424 11,562 Employee benefits 8,603 17,187 Deferred revenue 5,134 6,382 Research and development credits 3,699 3,889 Allowance for doubtful accounts 1,462 2,078 Other 2,003 3,114 Valuation allowance (1,906 ) (1,625 ) 73,635 99,208 Deferred tax liabilities: Other intangible assets (29,924 ) (56,195 ) Property and equipment (1,557 ) (2,994 ) Unremitted foreign earnings (1,504 ) 49 (32,985 ) (59,140 ) Net deferred tax assets $ 40,650 $ 40,068 At December 31, 2017 and 2016, respectively, the Company excluded from the above table deferred tax assets associated with foreign net operating loss carryforwards of $25.2 million and $13.2 million and corresponding valuation allowances of $25.2 million and $13.2 million in a jurisdiction where the Company determined utilization is remote. The net increase in the valuation allowance was primarily due to a change in circumstances related to the ability to utilize a net operating loss in a foreign jurisdiction. As of each reporting date, management considers new evidence, both positive and negative, that could affect the future realization of deferred tax assets. If management determines it is more likely than not that an asset, or a portion of an asset, will not be realized, a valuation allowance is recorded. As of December 31, 2017 , the Company had federal net operating loss carryforwards of $16.7 million . These losses expire between 2024 - 2034 , and are subject to limitations on their utilization. Deferred tax assets of $0.6 million have been recorded for state operating loss carryforwards. These losses expire between 2025 - 2035 , and are subject to limitations on their utilization. The Company had total foreign net operating loss carryforwards of $66.4 million , of which $29.6 million are not currently subject to expiration dates. The remainder, $36.8 million , expires between 2019 - 2034 . The Company had tax credit carryforwards of $4.6 million , of which $2.3 million are subject to limitations on their utilization. Approximately $0.6 million of these tax credit carryforwards are not currently subject to expiration dates. The remainder, $4.0 million , expires in various years between 2019 - 2037 . The following is a reconciliation of the total amounts of unrecognized tax benefits: Year Ended December 31, (in thousands) 2017 2016 2015 Unrecognized tax benefit as of January 1 $ 15,209 $ 16,067 $ 16,342 Gross increases—tax positions in prior period 905 983 64 Gross decreases—tax positions in prior period (765 ) (2,502 ) (850 ) Gross increases—tax positions in current period 3,757 2,725 4,064 Reductions due to a lapse of the applicable statute of limitations (847 ) (927 ) (2,808 ) Changes due to currency fluctuation 1,414 (348 ) (653 ) Settlements (16 ) (789 ) (92 ) Unrecognized tax benefit as of December 31 $ 19,657 $ 15,209 $ 16,067 The Company believes that it is reasonably possible that approximately $0.8 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, 2017 , $11.7 million would affect the effective tax rate, if recognized. The Company recognizes interest and penalties related to income taxes as income tax expense. During the years ended December 31, 2017 , 2016 and 2015, the Company recorded penalty expense of $1.1 million , $0.8 million and $0.3 million , respectively. The Company recorded interest expense of $0.4 million and $0.1 million during the years ended December 31, 2017 and 2016, respectively. As of December 31, 2017 , the Company accrued a liability for penalties of $3.9 million and interest of $3.6 million . As of December 31, 2016 , the Company accrued a liability for penalties of $2.7 million and interest of $2.8 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 2014 - 2017 tax years are open to examination by the Internal Revenue Service.

Pension And Profit-Sharing Plan

Pension And Profit-Sharing Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Pension And Profit-Sharing Plans	Pension and Profit-Sharing Plans The Company has a 401(k)/profit-sharing plan for all qualifying 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 meets the minimum statutory funding requirements for its foreign defined benefit and contribution plans. 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 $10.1 million in 2017 , $9.1 million in 2016 and $8.4 million in 2015 .

Non-Compete and Employment Agre

Non-Compete and Employment Agreements	12 Months Ended
	Dec. 31, 2017
Non-Compete and Employment Agreements [Abstract]
Non-Compete and Employment Agreements	Non-Compete and Employment Agreements Employees of the Company have signed agreements under which they have agreed not to disclose trade secrets or confidential information that, where legally permitted, restrict engagement in or connection with any business that is competitive with the Company anywhere in the world while employed by the Company (and, in some cases, for specified periods thereafter in relevant geographic areas), and that any products or technology created by them during their term of employment are the property of the Company. In addition, the Company requires all channel partners to enter into agreements not to disclose the Company's trade secrets and other proprietary information. The Company has an employment agreement with the Chief Executive Officer. This agreement provides for, among other things, in the case of termination for reasons other than death, disability or cause and subject to non-compete and non-solicit clauses, minimum severance payments equal to two times his base salary and target bonus paid out over two years from the date of termination and up to two years of payments for health care coverage from the date of termination. The Chief Executive Officer is subject to a two-year restriction on competition and solicitation following termination of employment under the circumstances described in the contract. The Company has a transition agreement with its Chairman of the Board. This agreement provides for, among other things, that the Chairman of the Board shall be employed by the Company until April 30, 2019 unless terminated earlier in accordance with the terms of the agreement. The Chairman of the Board shall receive salary paid in bi-monthly installments as specified in the transition agreement and restricted stock units vesting in part in February 2018 and the remainder at the end of the transition agreement, subject to the Chairman of the Board's continued employment, in accordance with the terms of the transition agreement. The Chairman of the Board will not be entitled to bonus payments during his employment pursuant to the transition agreement, but he will be eligible to participate in all of the Company’s benefit plans subject to the terms of such plans. The transition agreement provides for an additional payment (less salary received and equity calculations as set forth in the transition agreement) in the event that the Chairman of the Board's employment is terminated without cause prior to April 30, 2019. The Company also has employment agreements with several other employees, primarily in foreign jurisdictions. The terms of these employment agreements generally include annual compensation, severance payment provisions and non-compete clauses.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation The Company has a stock option and grant plan—the Fifth Amended and Restated 1996 Stock Option and Grant Plan (Stock Plan). The Stock Plan, as amended, authorizes the grant of up to 39.8 million shares of the Company's common stock in the form of: (i) incentive stock options (ISOs), (ii) nonqualified stock options, (iii) common stock with or without vesting or other restrictions, (iv) common stock upon the attainment of specified performance goals, (v) restricted stock awards, (vi) the right to receive cash dividends with the holders of the common stock as if the recipient held a specified number of shares of the common stock, (vii) deferred stock awards, (viii) restricted stock unit awards, (ix) stock appreciation rights and (x) cash-based awards. The Stock Plan provides that: (i) the exercise price of an ISO must be no less than the fair value of the stock at the date of grant and (ii) the exercise price of an ISO held by an optionee who possesses more than 10% of the total combined voting power of all classes of stock must be no less than 110% of the fair market value of the stock at the time of grant. The Compensation Committee of the Board of Directors has the authority to set expiration dates no later than ten years from the date of grant (or five years for an optionee who meets the 10% criterion), payment terms, and other provisions for each grant. The majority of options granted have a four -year vesting period. Shares associated with unexercised options or reacquired shares of common stock (except those shares withheld as a result of tax withholding or net issuance) become available for option grants and common stock issuances under the Stock Plan. The Compensation Committee of the Board of Directors may, at its sole discretion, accelerate or extend the date or dates on which all or any particular award or awards granted under the Stock Plan may vest or be exercised. In the event of a "sale event," defined in the Stock Plan as a "Transaction," all outstanding awards will be assumed or continued by the successor entity, with appropriate adjustment in the awards to reflect the transaction. In such event, except as the Compensation Committee may otherwise specify with respect to particular awards in the award agreements, if the service relationship of the holder of an award is terminated without cause within 18 months after the sale event, then all awards held by such holder will become fully vested and exercisable at that time. If there is a sale event in which the successor entity refuses to assume or continue outstanding awards, then subject to the consummation of the sale event, all awards with time-based vesting conditions will become fully vested and exercisable at the effective time of the sale event and all awards with performance-based vesting conditions may become vested and exercisable in accordance with the award agreements at the discretion of the Compensation Committee. If awards are not assumed or continued after a sale event, then all such awards will terminate at the time of the sale event. In the event of the termination of stock options or stock appreciation rights in connection with a sale event, the Compensation Committee may either make or provide for a cash payment to the holders of such awards equal to the difference between the per share transaction consideration and the exercise price of such awards or permit each holder to have at least a 15 -day period to exercise such awards prior to their termination. The Company currently issues shares related to exercised stock options or vested awards from its existing pool of treasury shares and has no specific policy to repurchase treasury shares as stock options are exercised or as awards vest. If the treasury pool is depleted, the Company will issue new shares. Total stock-based compensation expense recognized for the years ended December 31, 2017 , 2016 and 2015 is as follows: Year Ended December 31, (in thousands, except per share amounts) 2017 2016 2015 Cost of sales: Software licenses $ 969 $ 701 $ 745 Maintenance and service 2,533 1,578 1,868 Operating expenses: Selling, general and administrative 30,817 15,990 17,153 Research and development 18,835 15,078 14,185 Stock-based compensation expense before taxes 53,154 33,347 33,951 Related income tax benefits (20,503 ) (10,538 ) (11,656 ) Stock-based compensation expense, net of taxes $ 32,651 $ 22,809 $ 22,295 Net impact on earnings per share: Basic earnings per share $ (0.38 ) $ (0.26 ) $ (0.25 ) Diluted earnings per share $ (0.38 ) $ (0.26 ) $ (0.24 ) Information regarding stock option transactions is summarized below: Year Ended December 31, 2017 2016 2015 (options in thousands) Options Weighted- Average Exercise Price Options Weighted- Average Exercise Price Options Weighted- Average Exercise Price Outstanding, beginning of year 3,136 $ 56.37 3,986 $ 51.07 4,932 $ 48.76 Granted — $ — 260 $ 94.38 57 $ 88.10 Issued pursuant to acquisitions — $ — — $ — 8 $ 12.26 Exercised (956 ) $ 49.78 (1,082 ) $ 45.57 (975 ) $ 40.52 Forfeited (10 ) $ 80.92 (28 ) $ 72.07 (36 ) $ 70.15 Outstanding, end of year 2,170 $ 59.17 3,136 $ 56.37 3,986 $ 51.07 Vested and Exercisable, end of year 1,930 $ 55.11 2,762 $ 51.80 3,539 $ 48.29 2017 2016 2015 Weighted-Average Remaining Contractual Term (in years) Outstanding 4.10 4.62 4.85 Vested and Exercisable 3.57 4.04 4.53 Aggregate Intrinsic Value (in thousands) Outstanding $ 191,895 $ 113,822 $ 165,131 Vested and Exercisable $ 178,456 $ 112,379 $ 156,487 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 2017 , 2016 and 2015 . 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, 2016 2015 Risk-free interest rate 1.19% to 1.93% 1.18% to 1.65% Expected dividend yield —% —% Expected volatility 24% 25% Expected term 5.7 years 5.6 years Weighted-average fair value per share $23.96 $30.83 The Company did not grant stock option awards in 2017. Forfeitures of awards are accounted for as they occur. The effect of pre-vesting forfeitures on the Company's recorded expense has historically been negligible due to the relatively low turnover of stock option holders. The Company's determination of fair value of share-based payment awards on the date of grant using an option pricing model is affected by the Company's stock price as well as assumptions regarding a number of variables. The total estimated grant-date fair values of stock options that vested during the years ended December 31, 2017 , 2016 and 2015 were $2.9 million , $7.4 million and $12.3 million , respectively. As of December 31, 2017 , total unrecognized estimated compensation cost related to unvested stock options granted prior to that date was $5.0 million , which is expected to be recognized over a weighted-average period of 1.8 years . The total intrinsic values of stock options exercised during the years ended December 31, 2017 , 2016 and 2015 were $58.5 million , $49.8 million and $47.1 million , respectively. As of December 31, 2017 , 0.2 million unvested options with an aggregate intrinsic value of $13.4 million are expected to vest and have a weighted-average exercise price of $91.71 and a weighted-average remaining contractual term of 8.3 years . The Company recorded cash received from the exercise of stock options of $47.6 million and net tax benefits related to stock activity of $20.5 million for the year ended December 31, 2017 . Information regarding stock options outstanding as of December 31, 2017 is summarized below: (options in thousands) Options Outstanding Options Exercisable Range of Exercise Prices Options Weighted- Weighted- Options Weighted- $5.91 - $40.89 437 1.74 $ 32.01 434 $ 32.15 $48.97 - $55.30 392 2.80 $ 49.11 392 $ 49.11 $58.67 492 3.85 $ 58.67 492 $ 58.67 $61.68 - $95.09 849 6.05 $ 78.06 612 $ 72.35 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 26,227 , 35,000 and 34,450 performance-based restricted stock units with a market condition in 2017 , 2016 and 2015 , respectively. The percentage of the award that vests is based on the Company's performance as measured by total shareholder return relative to the 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. As of December 31, 2017 , 33,187 units of the total 2015 awards granted were earned and will be issued in 2018. 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 2017 , 2016 and 2015 was estimated on the grant date to be $120.94 , $78.71 and $81.61 , 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, 2017 , 2016 and 2015 was $1.8 million , $2.2 million and $3.1 million , respectively. The table below represents the assumptions used in the Monte Carlo simulation model to determine the fair value of the restricted stock units during each respective year: Year Ended December 31, Assumptions used in Monte Carlo lattice pricing model 2017 2016 2015 Risk-free interest rate 1.5% 1.0% 1.1% Expected dividend yield —% —% —% Expected volatility—ANSYS stock price 19% 21% 23% Expected volatility—NASDAQ Composite Index 15% 16% 14% Expected term 2.8 years 2.8 years 2.8 years Correlation factor 0.70 0.65 0.60 The Company issued 104,910 , 35,000 and 115,485 performance-based restricted stock awards during 2017 , 2016 and 2015 , respectively. Of the cumulative performance-based restricted stock awards issued, defined operating metrics were assigned to 85,132 , 63,462 and 51,795 awards with grant-date fair values of $106.95 , $84.61 and $86.38 during 2017 , 2016 and 2015 , respectively. 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. As of December 31, 2017 , 11,059 units of the total 2015 awards granted were earned and will be issued in 2018. As of December 31, 2017 , a total of 69,908 units of the 2017 awards granted were earned and of this total, 34,954 units will be issued in 2018 and 34,954 will be issued in 2020. Total compensation expense associated with the awards recorded for the years ended December 31, 2017 , 2016 and 2015 was $6.6 million, $0.4 million and $0.4 million , respectively. In addition, in 2017 , 2016 and 2015 , the Company granted restricted stock units of 762,732 , 488,622 and 344,500 , respectively, that will vest over a three - or four -year period with weighted-average grant-date fair values of $109.56 , $88.51 and $86.34 , respectively. During 2017 , 2016 and 2015, 261,618 , 162,019 and 85,713 shares vested and were released, respectively. As of December 31, 2017 , 2016 and 2015 , 1,262,496 , 838,327 and 571,462 units were outstanding, respectively. Total compensation expense is being recorded over the service period and was $37.3 million, $19.1 million and $12.5 million for the years ended December 31, 2017 , 2016 and 2015 , 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. Total compensation expense associated with the awards recorded for the years ended December 31, 2017 , 2016 and 2015 was $0.6 million , $1.2 million and $0.6 million , respectively. The Company has granted deferred stock awards to non-affiliate Independent Directors, which are rights to receive shares of common stock upon termination of service as a Director. In 2015 and prior, the deferred stock awards were granted quarterly in arrears and vested immediately upon grant. Associated with these awards, the Company established a non-qualified 409(a) deferred compensation plan with assets held under a rabbi trust to provide Directors an opportunity to diversify their vested awards. During open trading windows and at their elective option, the Directors may convert their Company shares into a variety of non-Company-stock investment options in order to diversify their holdings. As of December 31, 2017 , 29,500 shares have been diversified and 159,599 undiversified deferred stock awards have vested with the underlying shares remaining unissued until the service termination of the respective Director owners. In 2017 and 2016 , the Company granted 18,018 and 38,400 deferred stock awards, respectively, which will vest in full on the one -year anniversary of the grant. Total compensation expense associated with the awards recorded for the years ended December 31, 2017 , 2016 and 2015 was $2.6 million, $1.9 million and $4.0 million, respectively.

Stock Repurchase Program

Stock Repurchase Program	12 Months Ended
	Dec. 31, 2017
Class of Stock Disclosures [Abstract]
Stock Repurchase Program	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) 2017 2016 2015 Number of shares repurchased 2,750 3,700 3,833 Average price paid per share $ 122.20 $ 90.90 $ 88.16 Total cost $ 336,042 $ 336,335 $ 337,910 In February 2018, 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, 2017 , 2.8 million shares remained available for repurchase under the program.

Employee Stock Purchase Plan

Employee Stock Purchase Plan	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [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 in May 2016 to increase the number of shares available for offerings to 1.8 million shares. The Purchase Plan is administered by the Compensation Committee. Offerings under the Purchase Plan commence on each February 1 and August 1, and have a duration of six months. An employee who owns or is deemed to own shares of stock representing in excess of 5% of the combined voting power of all classes of stock of the Company may not participate in the Purchase Plan. During each offering, an eligible employee may purchase shares under the Purchase Plan by authorizing payroll deductions of up to 10% of his or her cash compensation during the offering period. The maximum number of shares that may be purchased by any participating employee during any offering period is limited to 3,840 shares (as adjusted by the Compensation Committee from time to time). Unless the employee has previously withdrawn from the offering, his or her accumulated payroll deductions will be used to purchase common stock on the last business day of the period at a price equal to 90% of the fair market value of the common stock on the first or last day of the offering period, whichever is lower. Under applicable tax rules, an employee may not accrue the right to purchase more than $25,000 of common stock, based on the grant-date fair value, in any calendar year in which the option is outstanding at any time. As of December 31, 2017 , 1.5 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, 2017 , 2016 and 2015 was $1.2 million , $1.2 million and $1.0 million , respectively.

Leases

Leases	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Leases	Leases Office Space The Company's executive offices and those related to certain domestic product development, marketing, production and administration are located in a 186,000 square foot office facility in Canonsburg, Pennsylvania. The term of the lease is 183 months , beginning on October 1, 2014 and expiring on December 31, 2029. Absent the exercise of options in the lease for additional rentable space or early lease termination, the Company's base rent (inclusive of property taxes and certain operating expenses) will be $4.3 million per annum for the first five years of the lease term, $4.5 million per annum for years six through ten and $4.7 million per annum for years eleven through fifteen. The Company incurred $4.4 million in lease expense related to this facility during each of the years ended December 31, 2017 , 2016 and 2015 . The Company has entered into various other noncancellable operating leases for office space. Office space lease expense totaled $17.1 million , $16.9 million and $16.5 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Future minimum lease payments, including termination fees, under noncancellable operating leases for office space in effect at December 31, 2017 are as follows: (in thousands) 2018 $ 14,139 2019 11,570 2020 8,785 2021 7,675 2022 7,046 Thereafter 15,898 Total $ 65,113

Royalty Agreements

Royalty Agreements	12 Months Ended
	Dec. 31, 2017
Royalty Agreements [Abstract]
Royalty Agreements	Royalty Agreements The Company has entered into various renewable, nonexclusive license agreements under which the Company has been granted access to the licensor's technology and the right to sell the technology in the Company's product line. Royalties are payable to developers of the software at various rates and amounts, which generally are based upon unit sales, revenue or flat fees. Royalty fees are reported in cost of goods sold and were $16.0 million , $13.1 million and $11.8 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Geographic Information

Geographic Information	12 Months Ended
	Dec. 31, 2017
Segments, Geographical Areas [Abstract]
Geographic Information	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) 2017 2016 2015 United States $ 417,342 $ 367,937 $ 354,433 Japan 126,262 120,160 104,299 Germany 108,216 99,814 94,546 South Korea 63,011 56,790 55,142 France 53,672 49,294 49,444 Canada 13,824 13,284 13,314 Other European 153,826 139,813 145,985 Other international 159,097 141,373 125,590 Total revenue $ 1,095,250 $ 988,465 $ 942,753 Property and equipment by geographic area is as follows: December 31, (in thousands) 2017 2016 United States $ 45,498 $ 43,810 Europe 5,059 4,753 India 3,704 3,033 Other international 2,835 3,081 Total property and equipment, net $ 57,096 $ 54,677

Unconditional Purchase Obligati

Unconditional Purchase Obligations	12 Months Ended
	Dec. 31, 2017
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 royalties, software licenses and long-term purchase contracts for network, communication and office maintenance services. The Company expended $14.1 million , $7.2 million and $5.3 million related to unconditional purchase obligations that existed as of the beginning of each year for the years ended December 31, 2017 , 2016 and 2015 , respectively. Future expenditures under unconditional purchase obligations in effect as of December 31, 2017 are as follows: (in thousands) 2018 $ 22,408 2019 18,271 2020 6,706 2021 4,545 2022 — Total $ 51,930

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Restructuring	During the fourth quarter of 2016, the Company initiated workforce realignment activities to reallocate resources to align with the Company's future strategic plans. The Company incurred related restructuring charges as follows: (in thousands) Gross Net of Tax Q4 2016 $ 3,419 $ 2,355 Q1 2017 9,273 6,176 Q2 2017 2,000 1,435 Q3 2017 466 331 Total restructuring charges $ 15,158 $ 10,297 The restructuring charges are included in the presentation of cost of software licenses; cost of maintenance and service; research and development expense; and selling, general and administrative expense. During the year ended December 31, 2017, the Company paid $12.5 million of the gross charges. As of December 31, 2017, $2.2 million of the gross charges incurred to date remains unpaid. The Company completed the workforce realignment activities as of September 30, 2017.

Contingencies and Commitments

Contingencies and Commitments	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Commitments	Contingencies and Commitments The Company is subject to various investigations, claims and legal proceedings that arise in the ordinary course of business, including commercial disputes, labor and employment matters, tax audits, alleged infringement of intellectual property rights and other matters. In the opinion of the Company, the resolution of pending matters is not expected to have a material adverse effect on the Company's consolidated results of operations, cash flows or financial position. However, each of these matters is subject to various uncertainties and it is possible that an unfavorable resolution of one or more of these proceedings could materially affect the Company's results of operations, cash flows or financial position. An Indian subsidiary of the Company has several service tax audits pending that have resulted in formal inquiries being received on transactions through mid-2012. The Company could incur tax charges and related liabilities of approximately $7.5 million . The service tax issues raised in the Company’s notices and inquiries are very similar to the case, M/s Microsoft Corporation (I) (P) Ltd. Vs Commissioner of Service Tax, New Delhi, wherein the Delhi Customs, Excise and Service Tax Appellate Tribunal (CESTAT) has passed a favorable ruling to Microsoft. The Company can provide no assurances on whether the Microsoft case’s favorable ruling will be challenged in higher courts or on the impact that the present Microsoft case’s decision will have on the Company’s cases. The Company is uncertain as to when these service tax matters will be concluded. A French subsidiary of the Company previously received notice that the French taxing authority rejected the Company's 2012 research and development credit. The Company contested the decision and received a favorable outcome during the first half of 2017. There are currently no challenges to other years' research and development credits for this subsidiary; however, other years are subject to future review and audit. 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, 2017 . 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 Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
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, 2017 $ 5,700 $ 1,474 $ 374 $ 6,800 Year ended December 31, 2016 $ 5,200 $ 2,009 $ 1,509 $ 5,700 Year ended December 31, 2015 $ 5,500 $ 1,304 $ 1,604 $ 5,200

Summary Of Significant Accounti

Summary Of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
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	The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements. Estimates also affect the amounts of revenue and expenses during the reported periods. Significant estimates included in these consolidated financial statements include: • Allowances for doubtful accounts receivable • Income tax accruals, including those related to the Tax Cuts and Jobs Act • Uncertain tax positions • Tax valuation reserves • Fair value of stock-based compensation and probabilities of performance award attainment • Contract revenue • Acquired deferred revenue • Useful lives for depreciation and amortization • Valuations of goodwill and other intangible assets • Deferred compensation • Loss contingencies Actual results could differ from these estimates. Changes in estimates are recorded in the results of operations in the period that the changes occur.
Revenue Recognition	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. The Company includes the revenue for the entire lease 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 funds. Cash equivalents are carried at cost, which approximates fair value. The Company's cash and cash equivalents balances comprise the following: December 31, 2017 December 31, 2016 (in thousands, except percentages) Amount % of Total Amount % of Total Cash accounts $ 568,587 64.5 $ 488,504 59.4 Money market funds 312,914 35.5 333,975 40.6 Total $ 881,501 $ 822,479 The Company's money market fund balances are held in various funds of a single issuer.
Property And Equipment	Property and equipment is stated at cost. Depreciation is computed using the straight-line method over the estimated useful lives of the various classes of assets, which range from one to forty years. Repairs and maintenance are charged to expense as incurred. Gains or losses from the sale or retirement of property and equipment are included in operating income.
Research And Development	Research and development costs, other than certain capitalized software development costs, are expensed as incurred.
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 and acquired software and technology. Intangible assets that are not considered to have an indefinite useful life are amortized over their useful lives, which are generally two to fifteen years. Amortization expense for intangible assets was $49.8 million , $50.8 million and $58.1 million for the years ended December 31, 2017 , 2016 and 2015 , 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 as of January 1 of each year unless there is an indicator that would require a test during the year. The Company periodically reviews the carrying value of other intangible assets and will recognize impairments when events or circumstances indicate that such assets may be impaired.
Concentrations Of Credit Risk	The Company has a concentration of credit risk with respect to revenue and trade receivables due to the use of certain significant channel partners to market and sell the Company's products. The Company performs periodic credit evaluations of its customers' financial condition and generally does not require collateral. The following table outlines concentrations of risk with respect to the Company's revenue: Year Ended December 31, (as a % of revenue) 2017 2016 2015 Revenue from channel partners 25 % 24 % 24 % Largest channel partner 5 % 5 % 5 % 2 nd largest channel partner 2 % 2 % 2 % No single customer accounted for more than 5% of the Company's revenue in 2017 , 2016 or 2015 . 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) 2017 2016 Cash and cash equivalents held domestically $ 561,417 $ 593,348 Cash and cash equivalents held by foreign subsidiaries 320,084 229,131 Cash and cash equivalents held in excess of deposit insurance, foreign and domestic 852,138 805,374 Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic 328,902 377,602
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 $1.5 million , $2.0 million and $1.3 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.
Income Taxes	The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period of the enactment date. The Company records net deferred tax assets to the extent it believes these assets will more likely than not be realized. In making such determination, the Company considers all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax planning strategies and recent financial operations. In the event the Company determines that it will be able to realize deferred tax assets for which a valuation allowance was used to reduce their carrying value, the adjustment to the valuation allowance will be recorded as a reduction to the provision for income taxes. Tax benefits related to uncertain tax positions taken or expected to be taken on a tax return are recorded when such benefits meet a more-likely-than-not threshold. Otherwise, these tax benefits are recorded when a tax position has been effectively settled, which means that the statute of limitations has expired or the appropriate taxing authority has completed its examination even though the statute of limitations remains open. The Company recognizes interest and penalties related to income taxes within the income tax expense line in the consolidated statements of income. Accrued interest and penalties are included within the related tax liability line in the consolidated balance sheets.
Foreign Currencies	Certain of the Company's sales and intercompany transactions are denominated in foreign currencies. These transactions are translated to the functional currency at the exchange rate on the transaction date. Assets and liabilities denominated in a currency other than the Company's or subsidiary's functional currency are translated at the effective exchange rate on the balance sheet date. Gains and losses resulting from foreign exchange transactions are included in other (expense) income, net. The Company recorded net foreign exchange losses of $1.9 million for the year ended December 31, 2017 , and net foreign exchange gains of $0.1 million and $0.5 million for the years ended December 31, 2016 and 2015 , 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 awards are anti-dilutive, they are excluded from the calculation of diluted EPS. The details of basic and diluted EPS are as follows: Year Ended December 31, (in thousands, except per share data) 2017 2016 2015 Net income $ 259,251 $ 265,636 $ 252,521 Weighted average shares outstanding – basic 84,988 87,227 89,561 Dilutive effect of stock plans 1,866 1,742 1,941 Weighted average shares outstanding – diluted 86,854 88,969 91,502 Basic earnings per share $ 3.05 $ 3.05 $ 2.82 Diluted earnings per share $ 2.98 $ 2.99 $ 2.76 Anti-dilutive shares 84 260 206
Stock-Based Compensation	The Company accounts for stock-based compensation in accordance with share-based payment accounting guidance. The guidance requires an entity to measure the cost of employee services received in exchange for an award of equity instruments based on the grant-date fair value of the award. The cost is recognized over the period during which an employee is required to provide service in exchange for the award, typically the vesting period.
Fair Value Of Financial Instruments	The Company accounts for certain assets and liabilities at fair value in accordance with the accounting guidance applicable to fair value measurements and disclosures. The carrying values of cash, cash equivalents, short-term investments, accounts receivable, accounts payable, accrued expenses, other accrued liabilities and short-term obligations are deemed to be reasonable estimates of their fair values because of their short-term nature.
New Accounting Guidance	Revenue from contracts with customers: In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (ASU 2014-09). ASU 2014-09 supersedes most current revenue recognition guidance, including industry-specific guidance. Previous 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. The standard also requires disclosure of the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. 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. This standard is effective for the Company on January 1, 2018. Entities have the option of using a full retrospective, cumulative effect or modified retrospective approach to adopt ASU 2014-09. The Company will utilize the modified retrospective implementation approach. The Company expects a cumulative-effect adjustment to increase retained earnings by $230.0 million - $260.0 million , or $165.0 million - $190.0 million net of income tax, on January 1, 2018, primarily derived from revenue related to software lease licenses. This update will impact the timing and amounts of revenue recognized, which will result in increased volatility in the amount of revenue recognized each period. The Company expects that the adoption of this standard will have a material impact on the Company’s consolidated financial statements. While the Company expects that the standard will impact various elements of its business, the most significant impact is expected to be on the recognition of revenue related to software lease licenses. These licenses include the right to use the software and PCS over the term of the license. These licenses are currently recognized as lease license revenue ratably over the term of the license. Under the new standard and the existing interpretations, the Company expects to recognize approximately 50% of the revenue related to these licenses up-front at the time the license is delivered. The up-front portion will continue to be reported within lease license revenue, but the ratable portion allocation to PCS will be reflected in maintenance revenue, resulting in a significant shift from software license revenue to maintenance and services revenue as reported on the consolidated statement of income. In addition, it is anticipated that there will be an acceleration of income tax payments associated with deferred revenue and backlog credited to retained earnings and never recognized as revenue in the financial statements. The 2018 acceleration of cash payments is expected to be between $15.0 million - $20.0 million . The Company has also made a preliminary assessment that the expense related to sales commissions will not be materially different under the new standard. However, the Company's preliminary assessments could change as additional interpretations relating to the new standard are provided and as issues identified by software industry groups are addressed. Leases: In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) (ASU 2016-02). ASU 2016-02 requires virtually all leases, other than leases that meet the definition of a short-term lease or leases of intangible assets, to be recorded on the balance sheet with a right-of-use asset and corresponding lease liability. Leases will be classified as either operating or finance leases based on certain criteria. This classification will determine the timing and presentation of expenses on the income statement, as well as the presentation of related cash flows. The standard is effective for annual periods beginning after December 15, 2018, including interim periods within that reporting period. Early adoption is permitted and a modified retrospective transition is required upon adoption. The Company does not expect to early adopt and continues to evaluate the effect that this update will have on its financial results upon adoption. The Company's preliminary assessment is that this update may materially increase the Company's assets and liabilities upon adoption. The Company has completed the initial inventory of its leases and policy elections, and the Company is currently developing new processes and controls to meet the accounting and disclosure requirements under the new standard. Employee share-based payment accounting: In March 2016, the FASB issued Accounting Standards Update No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (ASU 2016-09). This update includes various areas for simplification related to aspects of the accounting for share-based payment transactions. One simplification is that the tax effects of share-based payment settlements will be recorded in the income statement. Prior guidance required tax windfalls at settlement, and tax shortfalls to the extent of previous windfalls, to be recorded in equity. This provision was required to be adopted prospectively. The Company adopted the guidance during the quarter ended March 31, 2017. The primary impact of adoption was the recognition of excess tax benefits in the Company's provision for income taxes rather than paid-in capital, which resulted in the recognition of excess tax benefits in the provision for income taxes of $13.3 million during the year ended December 31, 2017. In addition, the Company applied the change in classification of such benefits from financing to operating on the consolidated statements of cash flows on a retrospective basis, resulting in an increase to both net cash provided by operating activities and net cash used in financing activities of $9.2 million and $8.2 million for the years ended December 31, 2016 and 2015, respectively. Credit losses: In June 2016, the FASB issued Accounting Standards Update No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13). Previous guidance requires the allowance for doubtful accounts to be estimated based on an incurred loss model, which considers past and current conditions. ASU 2016-13 requires companies to use an expected loss model that also considers reasonable and supportable forecasts of future conditions. ASU 2016-13 is effective for annual periods beginning after December 15, 2019, including interim periods within that reporting period. Early adoption is permitted for annual periods beginning after December 15, 2018, including interim periods within that reporting period. The standard requires a cumulative-effect adjustment to the statement of financial position as of the beginning of the first reporting period in which the guidance is effective. The Company is currently evaluating the effect that this update will have on its financial results upon adoption. Income taxes: In October 2016, the FASB issued Accounting Standards Update No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (ASU 2016-16). Previous guidance requires the tax effects from intra-entity asset transfers to be deferred until the asset is sold to a third party or recovered through use. ASU 2016-16 eliminates this deferral for all intra-entity asset transfers other than inventory. The standard is effective for annual periods beginning after December 15, 2017, including interim periods within that reporting period. Early adoption is permitted and a modified retrospective transition is required upon adoption. The Company plans to adopt ASU 2016-16 effective January 1, 2018 and expects adoption to have an immaterial effect, if any, on its financial results. Business combinations: In January 2017, the FASB issued Accounting Standards Update No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business (ASU 2017-01). This update narrows the definition of a business. If substantially all the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets, the acquiree is not a business. The update also requires a business to include an input and a substantive process that significantly contributes to the ability to create outputs. This definition is expected to reduce the number of acquisitions accounted for as business combinations, which will impact the accounting treatment of certain items, including the accounting treatment of contingent consideration and transaction expenses. ASU 2017-01 is effective for annual periods beginning after December 15, 2017, including interim periods within that reporting period. Early adoption is permitted and the update will be applied prospectively. The effect of the implementation will depend upon the nature of the Company's future acquisitions, if any. Historically, the Company has entered into acquisitions that would meet the definition of a business under ASU 2017-01. The Company plans to adopt ASU 2017-01 effective January 1, 2018.

Summary Of Significant Accoun30

Summary Of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Summary Of Cash And Cash Equivalents	The Company's cash and cash equivalents balances comprise the following: December 31, 2017 December 31, 2016 (in thousands, except percentages) Amount % of Total Amount % of Total Cash accounts $ 568,587 64.5 $ 488,504 59.4 Money market funds 312,914 35.5 333,975 40.6 Total $ 881,501 $ 822,479
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) 2017 2016 2015 Net income $ 259,251 $ 265,636 $ 252,521 Weighted average shares outstanding – basic 84,988 87,227 89,561 Dilutive effect of stock plans 1,866 1,742 1,941 Weighted average shares outstanding – diluted 86,854 88,969 91,502 Basic earnings per share $ 3.05 $ 3.05 $ 2.82 Diluted earnings per share $ 2.98 $ 2.99 $ 2.76 Anti-dilutive shares 84 260 206
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) 2017 2016 2015 Revenue from channel partners 25 % 24 % 24 % Largest channel partner 5 % 5 % 5 % 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) 2017 2016 Cash and cash equivalents held domestically $ 561,417 $ 593,348 Cash and cash equivalents held by foreign subsidiaries 320,084 229,131 Cash and cash equivalents held in excess of deposit insurance, foreign and domestic 852,138 805,374 Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic 328,902 377,602

Other Receivables and Current31

Other Receivables and Current Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Prepaid Expense and Other Assets, Current [Abstract]
Schedule of Other Receivables and Current Assets	The Company's other receivables and current assets comprise the following balances: December 31, (in thousands) 2017 2016 Receivables related to unrecognized revenue $ 215,155 $ 199,119 Income taxes receivable, including overpayments and refunds 21,663 15,718 Prepaid expenses and other current assets 27,002 24,512 Total other receivables and current assets $ 263,820 $ 239,349

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Components Of Property and Equipment	Property and equipment consists of the following: December 31, (in thousands) Estimated Useful Lives 2017 2016 Equipment 1-10 years $ 88,189 $ 78,614 Computer software 1-5 years 34,994 30,867 Buildings and improvements 5-40 years 26,423 25,472 Leasehold improvements 1-16 years 13,316 11,571 Furniture 1-13 years 9,239 8,618 Land 1,759 1,759 Property and equipment, gross 173,920 156,901 Less: Accumulated depreciation (116,824 ) (102,224 ) Property and equipment, net $ 57,096 $ 54,677

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 December 31, 2016 (in thousands) Gross Carrying Amount Accumulated Amortization Gross Carrying Amount Accumulated Amortization Finite-lived intangible assets: Developed software and core technologies (3 – 11 years) $ 365,317 $ (297,645 ) $ 338,594 $ (275,130 ) Customer lists and contract backlog (5 – 15 years) 171,048 (104,522 ) 159,549 (88,414 ) Trade names (2 – 10 years) 127,200 (104,130 ) 127,952 (90,289 ) Total $ 663,565 $ (506,297 ) $ 626,095 $ (453,833 ) Indefinite-lived intangible assets: Trade name $ 357 $ 357
Estimated Future Amortization Expense for Intangible Assets	As of December 31, 2017 , estimated future amortization expense for the intangible assets reflected above is as follows: (in thousands) 2018 $ 39,162 2019 26,362 2020 25,449 2021 21,225 2022 16,197 Thereafter 28,873 Total intangible assets subject to amortization, net 157,268 Indefinite-lived trade name 357 Other intangible assets, net $ 157,625
Changes in Goodwill	The changes in goodwill during the years ended December 31, 2017 and 2016 are as follows: (in thousands) 2017 2016 Beginning balance - January 1 $ 1,337,215 $ 1,332,348 Acquisitions 36,554 6,184 Adjustments (1) (111 ) (1 ) Currency translation 4,895 (1,316 ) Ending balance - December 31 $ 1,378,553 $ 1,337,215 (1) In accordance with the accounting for business combinations, the Company recorded adjustments to goodwill for the effect of changes in the provisional fair values of the assets acquired and liabilities assumed during the measurement period (up to one year from the acquisition date) as the Company obtained new information about facts and circumstances that existed as of the acquisition date that, if known, would have affected the measurement of the amounts recognized as of that date.

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities Measured on Recurring Basis	The following tables provide the assets carried at fair value and measured on a recurring basis: Fair Value Measurements at Reporting Date Using: (in thousands) December 31, 2017 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Cash equivalents $ 312,914 $ 312,914 $ — $ — Short-term investments $ 286 $ — $ 286 $ — Deferred compensation plan investments $ 3,742 $ 3,742 $ — $ — Fair Value Measurements at Reporting Date Using: (in thousands) December 31, 2016 Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Cash equivalents $ 333,975 $ 333,975 $ — $ — Short-term investments $ 381 $ — $ 381 $ — Deferred compensation plan investments $ 459 $ 459 $ — $ —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Components Of Income Before Income Taxes	Income before income taxes includes the following components: Year Ended December 31, (in thousands) 2017 2016 2015 Domestic $ 344,447 $ 340,251 $ 325,097 Foreign 51,247 40,064 31,668 Total $ 395,694 $ 380,315 $ 356,765
Components Of Provision For Income Taxes	The provision for income taxes is composed of the following: Year Ended December 31, (in thousands) 2017 2016 2015 Current: Federal $ 112,414 $ 99,783 $ 93,853 State 7,879 8,338 7,733 Foreign 18,843 17,479 17,854 Deferred: Federal (7,387 ) (13,368 ) (14,472 ) State (584 ) (1,036 ) (1,987 ) Foreign 5,278 3,483 1,263 Total $ 136,443 $ 114,679 $ 104,244
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, 2017 2016 2015 Federal statutory tax rate 35.0 % 35.0 % 35.0 % U.S. tax reform 4.5 — — State income taxes, net of federal benefit 1.1 1.6 1.1 Uncertain tax positions 0.3 (0.2 ) (0.4 ) Benefit from restructuring activities — (2.2 ) (2.7 ) Research and development credits (1.4 ) (1.0 ) (1.1 ) Domestic production activity benefit (2.6 ) (3.7 ) (3.1 ) Stock-based compensation (3.1 ) 0.2 — Other 0.7 0.5 0.4 34.5 % 30.2 % 29.2 %
Components Of Deferred Tax Assets And Liabilities	The components of deferred tax assets and liabilities are as follows: December 31, (in thousands) 2017 2016 Deferred tax assets: Net operating loss carryforwards $ 21,391 $ 32,969 Stock-based compensation 17,825 23,652 Uncertain tax positions 15,424 11,562 Employee benefits 8,603 17,187 Deferred revenue 5,134 6,382 Research and development credits 3,699 3,889 Allowance for doubtful accounts 1,462 2,078 Other 2,003 3,114 Valuation allowance (1,906 ) (1,625 ) 73,635 99,208 Deferred tax liabilities: Other intangible assets (29,924 ) (56,195 ) Property and equipment (1,557 ) (2,994 ) Unremitted foreign earnings (1,504 ) 49 (32,985 ) (59,140 ) Net deferred tax assets $ 40,650 $ 40,068
Reconciliation Of Unrecognized Tax Benefits	The following is a reconciliation of the total amounts of unrecognized tax benefits: Year Ended December 31, (in thousands) 2017 2016 2015 Unrecognized tax benefit as of January 1 $ 15,209 $ 16,067 $ 16,342 Gross increases—tax positions in prior period 905 983 64 Gross decreases—tax positions in prior period (765 ) (2,502 ) (850 ) Gross increases—tax positions in current period 3,757 2,725 4,064 Reductions due to a lapse of the applicable statute of limitations (847 ) (927 ) (2,808 ) Changes due to currency fluctuation 1,414 (348 ) (653 ) Settlements (16 ) (789 ) (92 ) Unrecognized tax benefit as of December 31 $ 19,657 $ 15,209 $ 16,067

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 , 2016 and 2015 is as follows: Year Ended December 31, (in thousands, except per share amounts) 2017 2016 2015 Cost of sales: Software licenses $ 969 $ 701 $ 745 Maintenance and service 2,533 1,578 1,868 Operating expenses: Selling, general and administrative 30,817 15,990 17,153 Research and development 18,835 15,078 14,185 Stock-based compensation expense before taxes 53,154 33,347 33,951 Related income tax benefits (20,503 ) (10,538 ) (11,656 ) Stock-based compensation expense, net of taxes $ 32,651 $ 22,809 $ 22,295 Net impact on earnings per share: Basic earnings per share $ (0.38 ) $ (0.26 ) $ (0.25 ) Diluted earnings per share $ (0.38 ) $ (0.26 ) $ (0.24 )
Summary Of Stock Options	Information regarding stock option transactions is summarized below: Year Ended December 31, 2017 2016 2015 (options in thousands) Options Weighted- Average Exercise Price Options Weighted- Average Exercise Price Options Weighted- Average Exercise Price Outstanding, beginning of year 3,136 $ 56.37 3,986 $ 51.07 4,932 $ 48.76 Granted — $ — 260 $ 94.38 57 $ 88.10 Issued pursuant to acquisitions — $ — — $ — 8 $ 12.26 Exercised (956 ) $ 49.78 (1,082 ) $ 45.57 (975 ) $ 40.52 Forfeited (10 ) $ 80.92 (28 ) $ 72.07 (36 ) $ 70.15 Outstanding, end of year 2,170 $ 59.17 3,136 $ 56.37 3,986 $ 51.07 Vested and Exercisable, end of year 1,930 $ 55.11 2,762 $ 51.80 3,539 $ 48.29 2017 2016 2015 Weighted-Average Remaining Contractual Term (in years) Outstanding 4.10 4.62 4.85 Vested and Exercisable 3.57 4.04 4.53 Aggregate Intrinsic Value (in thousands) Outstanding $ 191,895 $ 113,822 $ 165,131 Vested and Exercisable $ 178,456 $ 112,379 $ 156,487
Information Regarding Stock Options Outstanding	Information regarding stock options outstanding as of December 31, 2017 is summarized below: (options in thousands) Options Outstanding Options Exercisable Range of Exercise Prices Options Weighted- Weighted- Options Weighted- $5.91 - $40.89 437 1.74 $ 32.01 434 $ 32.15 $48.97 - $55.30 392 2.80 $ 49.11 392 $ 49.11 $58.67 492 3.85 $ 58.67 492 $ 58.67 $61.68 - $95.09 849 6.05 $ 78.06 612 $ 72.35
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, 2016 2015 Risk-free interest rate 1.19% to 1.93% 1.18% to 1.65% Expected dividend yield —% —% Expected volatility 24% 25% Expected term 5.7 years 5.6 years Weighted-average fair value per share $23.96 $30.83
Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Assumptions To Estimate Fair Value Of Stock Awards	The table below represents the assumptions used in the Monte Carlo simulation model to determine the fair value of the restricted stock units during each respective year: Year Ended December 31, Assumptions used in Monte Carlo lattice pricing model 2017 2016 2015 Risk-free interest rate 1.5% 1.0% 1.1% Expected dividend yield —% —% —% Expected volatility—ANSYS stock price 19% 21% 23% Expected volatility—NASDAQ Composite Index 15% 16% 14% Expected term 2.8 years 2.8 years 2.8 years Correlation factor 0.70 0.65 0.60

Stock Repurchase Program (Table

Stock Repurchase Program (Tables)	12 Months Ended
	Dec. 31, 2017
Class of Stock Disclosures [Abstract]
Stock Repurchase Program	Under the Company's stock repurchase program, the Company repurchased shares as follows: Year Ended December 31, (in thousands, except per share data) 2017 2016 2015 Number of shares repurchased 2,750 3,700 3,833 Average price paid per share $ 122.20 $ 90.90 $ 88.16 Total cost $ 336,042 $ 336,335 $ 337,910

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	Future minimum lease payments, including termination fees, under noncancellable operating leases for office space in effect at December 31, 2017 are as follows: (in thousands) 2018 $ 14,139 2019 11,570 2020 8,785 2021 7,675 2022 7,046 Thereafter 15,898 Total $ 65,113

Geographic Information (Tables)

Geographic Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segments, Geographical Areas [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) 2017 2016 2015 United States $ 417,342 $ 367,937 $ 354,433 Japan 126,262 120,160 104,299 Germany 108,216 99,814 94,546 South Korea 63,011 56,790 55,142 France 53,672 49,294 49,444 Canada 13,824 13,284 13,314 Other European 153,826 139,813 145,985 Other international 159,097 141,373 125,590 Total revenue $ 1,095,250 $ 988,465 $ 942,753
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) 2017 2016 United States $ 45,498 $ 43,810 Europe 5,059 4,753 India 3,704 3,033 Other international 2,835 3,081 Total property and equipment, net $ 57,096 $ 54,677

Unconditional Purchase Obliga40

Unconditional Purchase Obligations (Tables)	12 Months Ended
	Dec. 31, 2017
Unconditional Purchase Obligations (Excluding Capital Stock Redemptions) [Abstract]
Unrecorded Unconditional Purchase Obligations Disclosure	Future expenditures under unconditional purchase obligations in effect as of December 31, 2017 are as follows: (in thousands) 2018 $ 22,408 2019 18,271 2020 6,706 2021 4,545 2022 — Total $ 51,930

Restructuring (Tables)

Restructuring (Tables)	12 Months Ended
	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Costs	The Company incurred related restructuring charges as follows: (in thousands) Gross Net of Tax Q4 2016 $ 3,419 $ 2,355 Q1 2017 9,273 6,176 Q2 2017 2,000 1,435 Q3 2017 466 331 Total restructuring charges $ 15,158 $ 10,297

Organization - Additional Infor

Organization - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017Segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	1

Summary Of Significant Accoun43

Summary Of Significant Accounting Policies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Amortization		$ 49,766	$ 50,847	$ 58,149
Provisions for doubtful accounts		1,474	2,009	1,304
Net foreign exchange (losses) gains		(1,935)	77	486
Income tax provision		136,443	114,679	104,244
Net cash provided by (used in) operating activities		430,438	365,980	375,699
Net cash provided by (used in) financing activities		(294,651)	$ (288,630)	$ (299,927)
Minimum [Member]
Cumulative effect of new accounting principle in period of adoption		$ 165,000
Semiconductor product licenses, term		24 months
Property and equipment, estimated useful lives (years)		1 year
Maximum [Member]
Cumulative effect of new accounting principle in period of adoption		$ 190,000
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
Scenario, Forecast [Member] | Minimum [Member]
Payments for other taxes	$ 15,000
Scenario, Forecast [Member] | Maximum [Member]
Payments for other taxes	$ 20,000
Gross Impact [Member] | Minimum [Member]
Cumulative effect of new accounting principle in period of adoption		$ 230,000
Gross Impact [Member] | Maximum [Member]
Cumulative effect of new accounting principle in period of adoption		260,000
Adjustments for New Accounting Pronouncement [Member]
Income tax provision		$ (13,300)
Net cash provided by (used in) operating activities			$ 0	$ 0
Net cash provided by (used in) financing activities			$ 0	$ 0

Summary Of Significant Accoun44

Summary Of Significant Accounting Policies (Summary Of Cash And Cash Equivalents) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Cash accounts	$ 568,587	$ 488,504
Money market funds	312,914	333,975
Cash and cash equivalents	$ 881,501	$ 822,479	$ 784,168	$ 788,064
Cash accounts, % of Total	64.50%	59.40%
Money market funds, % of Total	35.50%	40.60%

Summary Of Significant Accoun45

Summary Of Significant Accounting Policies (Schedule Of Risk Concentration) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Concentration Risk [Line Items]
Cash and cash equivalents, at carrying value	$ 881,501	$ 822,479	$ 784,168	$ 788,064
Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Channel partner concentration risk, percentage	24.70%	24.40%	24.20%
Credit Concentration Risk [Member]
Concentration Risk [Line Items]
Cash and cash equivalents held in excess of deposit insurance, foreign and domestic	$ 852,138	$ 805,374
Largest balance of cash and cash equivalents held with one financial institution, foreign and domestic	$ 328,902	$ 377,602
1st Largest Channel Partner [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Channel partner concentration risk, percentage	5.00%	5.00%	5.00%
2nd Largest Channel Partner [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Channel partner 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	$ 561,417	$ 593,348
FOREIGN | Credit Concentration Risk [Member]
Concentration Risk [Line Items]
Cash and cash equivalents, at carrying value	$ 320,084	$ 229,131

Summary Of Significant Accoun46

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, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Net income	$ 259,251	$ 265,636	$ 252,521
Weighted average shares outstanding - basic	84,988	87,227	89,561
Dilutive effect of stock plans	1,866	1,742	1,941
Weighted average shares outstanding - diluted	86,854	88,969	91,502
Basic earnings per share	$ 3.05	$ 3.05	$ 2.82
Diluted earnings per share	$ 2.98	$ 2.99	$ 2.76
Anti-dilutive shares	84	260	206

Acquisition - Additional Inform

Acquisition - Additional Information (Detail) - Series of Individually Immaterial Business Acquisitions [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Total consideration transferred at fair value	$ 67,000	$ 10,300	$ 49,700
Acquired deferred revenue, impact on reported revenue	$ 2,856	$ 100	$ 800

Other Receivables and Current48

Other Receivables and Current Assets - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other receivables and current assets	$ 263,820	$ 239,349
Receivables related to unrecognized revenue
Other receivables and current assets	215,155	199,119
Income taxes receivable, including overpayments and refunds
Other receivables and current assets	21,663	15,718
Prepaid expenses and other current assets
Other receivables and current assets	$ 27,002	$ 24,512

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Depreciation expense related to property and equipment	$ 17.9	$ 18.7	$ 19.5

Property and Equipment (Compone

Property and Equipment (Components Of Property and Equipment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 173,920	$ 156,901
Less: Accumulated depreciation	(116,824)	(102,224)
Property and equipment, net	57,096	54,677
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	88,189	78,614
Computer Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	34,994	30,867
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	26,423	25,472
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	13,316	11,571
Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	9,239	8,618
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,759	$ 1,759
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] | Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	5 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] | Building and Building Improvements [Member]
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)	16 years
Maximum [Member] | Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives (years)	13 years

Intangible Assets (Detail)

Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	$ 663,565	$ 626,095
Amortized intangible assets, accumulated amortization	(506,297)	(453,833)
Unamortized intangible assets, gross carrying amount	357
Developed Software and Core Technologies
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	365,317	338,594
Amortized intangible assets, accumulated amortization	(297,645)	(275,130)
Customer Lists and Contract Backlog
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	171,048	159,549
Amortized intangible assets, accumulated amortization	(104,522)	(88,414)
Trade Names
Intangible Assets [Line Items]
Amortized intangible assets, gross carrying amount	127,200	127,952
Amortized intangible assets, accumulated amortization	(104,130)	(90,289)
Trade Names
Intangible Assets [Line Items]
Unamortized intangible assets, gross carrying amount	$ 357	$ 357

Estimated Useful Lives (Detail)

Estimated Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2017
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 Asset53

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization	$ 49,766	$ 50,847	$ 58,149

Estimated Future Amortization E

Estimated Future Amortization Expense for Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
2,018	$ 39,162
2,019	26,362
2,020	25,449
2,021	21,225
2,022	16,197
Thereafter	28,873
Total intangible assets subject to amortization, net	157,268
Indefinite-lived trade name	357
Other intangible assets, net	$ 157,625	$ 172,619

Changes in Goodwill (Detail)

Changes in Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Beginning balance	$ 1,337,215	$ 1,332,348
Acquisitions	36,554	6,184
Adjustments	(111)	(1)
Currency translation	4,895	(1,316)
Ending balance	$ 1,378,553	$ 1,337,215

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 312,914	$ 333,975
Short-term investments	286	381
Deferred compensation plan investments	3,742	459
Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	312,914	333,975
Short-term investments	0	0
Deferred compensation plan investments	3,742	459
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	286	381
Deferred compensation plan investments	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Short-term investments	0	0
Deferred compensation plan investments	$ 0	$ 0

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017
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	12 months

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		35.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount		$ 17,900
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount		1,900
Deferred tax assets, operating loss carryforwards, foreign		25,200	$ 13,200
Deferred tax assets, valuation allowance		1,906	1,625
Deferred tax assets, operating loss carryforwards, state and local		600
Tax credit carryforwards		4,600
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit		800
Unrecognized tax benefits that would impact effective tax rate		11,700
Penalty expense		1,100	800	$ 300
Interest expense		400	100
Liability for penalties		3,900	2,700
Liability for interest		3,600	2,800
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount		16,000
Accrued income taxes, long-term		14,500
Subject To Expiration [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards		4,000
Subject To Utilization Limitations [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards		2,300
Not Subject To Expiration [Member]
Income Tax Contingency [Line Items]
Tax credit carryforwards		600
Foreign Country [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards		66,400
Federal Domestic [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards		16,700
Operating Loss Carryforward With No Expiration Date [Member] | Foreign Country [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards		29,600
Subject To Expiration [Member] | Foreign Country [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards		$ 36,800
Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Tax credit carryforward, expiration date		Jan. 1, 2019
Years open to examination		2,014
Earliest Tax Year [Member] | Foreign Country [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date		Jan. 1, 2019
Earliest Tax Year [Member] | Federal Domestic [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date		Jan. 1, 2024
Earliest Tax Year [Member] | State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date		Jan. 1, 2025
Latest Tax Year [Member]
Income Tax Contingency [Line Items]
Tax credit carryforward, expiration date		Dec. 31, 2037
Years open to examination		2,017
Latest Tax Year [Member] | Foreign Country [Member]
Income Tax Contingency [Line Items]
Operating loss carryforwards, expiration date		Dec. 31, 2034
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
Valuation Allowance, Operating Loss Carryforwards [Member] | Foreign Country [Member]
Income Tax Contingency [Line Items]
Deferred tax assets, valuation allowance		$ 25,200	$ 13,200
Maximum [Member]
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, Deduction, Percent		50.00%
Scenario, Forecast [Member]
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%

Income Taxes (Components Of Inc

Income Taxes (Components Of Income Before Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic	$ 344,447	$ 340,251	$ 325,097
Foreign	51,247	40,064	31,668
Income before income tax provision	$ 395,694	$ 380,315	$ 356,765

Income Taxes (Components Of Pro

Income Taxes (Components Of Provision For Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current, Federal	$ 112,414	$ 99,783	$ 93,853
Current, State	7,879	8,338	7,733
Current, Foreign	18,843	17,479	17,854
Deferred, Federal	(7,387)	(13,368)	(14,472)
Deferred, State	(584)	(1,036)	(1,987)
Deferred, Foreign	5,278	3,483	1,263
Total	$ 136,443	$ 114,679	$ 104,244

Income Taxes (Reconciliation Of

Income Taxes (Reconciliation Of U.S. Federal Statutory Tax Rate To Consolidated Effective Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal statutory tax rate	35.00%	35.00%	35.00%
U.S. tax reform	4.50%	0.00%	0.00%
State income taxes, net of federal benefit	1.10%	1.60%	1.10%
Uncertain tax positions	0.30%	(0.20%)	(0.40%)
Benefit from restructuring activities	(0.00%)	(2.20%)	(2.70%)
Research and development credits	(1.40%)	(1.00%)	(1.10%)
Domestic production activity benefit	(2.60%)	(3.70%)	(3.10%)
Stock-based compensation	3.10%
Stock-based compensation		(0.20%)	(0.00%)
Other	0.70%	0.50%	0.40%
Consolidated effective tax rate	34.50%	30.20%	29.20%

Income Taxes (Components Of Def

Income Taxes (Components Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 21,391	$ 32,969
Stock-based compensation	17,825	23,652
Uncertain tax positions	15,424	11,562
Employee benefits	8,603	17,187
Deferred revenue	5,134	6,382
Research and development credits	3,699	3,889
Allowance for doubtful accounts	1,462	2,078
Other	2,003	3,114
Valuation allowance	(1,906)	(1,625)
Deferred tax assets	73,635	99,208
Other intangible assets	(29,924)	(56,195)
Property and equipment	(1,557)	(2,994)
Unremitted foreign earnings	(1,504)
Unremitted foreign earnings		49
Deferred tax liabilities	(32,985)	(59,140)
Net deferred tax assets	$ 40,650	$ 40,068

Income Taxes (Reconciliation 63

Income Taxes (Reconciliation Of Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefit as of January 1	$ 15,209	$ 16,067	$ 16,342
Gross increases-tax positions in prior period	905	983	64
Gross decreases-tax positions in prior period	(765)	(2,502)	(850)
Gross increases-tax positions in current period	3,757	2,725	4,064
Reductions due to a lapse of the applicable statute of limitations	(847)	(927)	(2,808)
Changes due to currency fluctuation	1,414
Changes due to currency fluctuation		(348)	(653)
Settlements	(16)	(789)	(92)
Unrecognized tax benefit as of December 31	$ 19,657	$ 15,209	$ 16,067

Pension And Profit-Sharing Pl64

Pension And Profit-Sharing Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Expenses related to retirement programs	$ 10.1	$ 9.1	$ 8.4
Four Zero One K Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Maximum annual contributions per employee, percent	4.25%
Minimum working hours per employee required to be eligible for discretionary contribution	1000 hours
First Three Percent Of Employee Pay [Member] | Four Zero One K Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of employee contribution employer matches	100.00%
Percentage of employee pay employer matches	3.00%
More Than Three Percent Up To Eight Percent Of Employee Pay [Member] | Four Zero One K Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of employee contribution employer matches	25.00%
Percentage of employee pay employer matches	5.00%

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares authorized for grant under the plan	39,800,000
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%
Vesting period	4 years
Maximum months after sale event where awards fully vest when service relationship terminated without cause	18 months
Minimum number of days that may be granted to terminated employee to exercise awards prior to termination	15 days
Share-based compensation arrangement by share-based payment award, options, vested in period, fair value	$ 2,900	$ 7,400	$ 12,300
Total unrecognized estimated unvested stock option compensation cost	$ 5,000
Weighted-average period of recognition of unrecognized compensation cost (years)	1 year 9 months
Total intrinsic value of options exercised during the period	$ 58,500	49,800	47,100
Unvested options	200,000
Aggregate intrinsic value of unvested options	$ 13,400
Weighted-average exercise price of unvested options	$ 91.71
Weighted-average remaining contractual term of unvested stock options (years)	8 years 3 months
Employee service share-based compensation, cash received from exercise of stock options	$ 47,600
Tax benefit from exercise of stock options	20,500
Stock-based compensation expense	53,154	33,347	33,951
Fair value of stock options and restricted stock awards assumed in connection with acquisitions	$ 0	$ 0	$ 3,528
Performance Shares [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of awards granted	26,227	35,000	34,450
Value of the restricted stock units on the grant date	$ 120.94	$ 78.71	$ 81.61
Stock-based compensation expense	$ 1,800	$ 2,200	$ 3,100
Restricted stock units earned	33,187
Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of awards granted	85,132	63,462	51,795
Value of the restricted stock units on the grant date	$ 106.95	$ 84.61	$ 86.38
Stock-based compensation expense	$ 6,600	$ 400	$ 400
Share-based compensation arrangement by share-based payment award, shares issued in period	104,910	35,000	115,485
Restricted stock units earned	11,059
Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of awards granted	762,732	488,622	344,500
Value of the restricted stock units on the grant date	$ 109.56	$ 88.51	$ 86.34
Stock-based compensation expense	$ 37,300	$ 19,100	$ 12,500
Restricted stock units earned	261,618	162,019	85,713
Share-based compensation arrangement by share-based payment award, equity instruments other than options, nonvested, number	1,262,496	838,327	571,462
Deferred Stock Units [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period	1 year
Number of awards granted	18,018	38,400
Stock-based compensation expense	$ 2,600	$ 1,900	$ 4,000
Restricted stock units earned	159,599
Diversified deferred stock awards	29,500
Series of Individually Immaterial Business 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
Stock-based compensation expense	$ 600	$ 1,200	$ 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
Minimum [Member] | Performance Shares [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period	1 year
Minimum [Member] | Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period	3 years
Maximum [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration period of options from the date of grant	10 years
Expiration period for optionee who meets the 10% criteria	5 years
Maximum [Member] | Performance Shares [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period	3 years
Maximum [Member] | Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period	4 years

Stock-Based Compensation (Summa

Stock-Based Compensation (Summary Of Stock Options) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning of year, Weighted-Average Exercise Price	$ 56.37	$ 51.07	$ 48.76
Granted, Weighted-Average Exercise Price	0	94.38	88.10
Issued pursuant to acquisitions, Weighted-Average Exercise Price	0	0	12.26
Exercised, Weighted-Average Exercise Price	49.78	45.57	40.52
Forfeited, Weighted-Average Exercise Price	80.92	72.07	70.15
Outstanding, end of year, Weighted-Average Exercise Price	59.17	56.37	51.07
Vested and Exercisable, end of year, Weighted-Average Exercise Price	$ 55.11	$ 51.80	$ 48.29
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning of year, Options	3,136	3,986	4,932
Granted, Options	0	260	57
Issued pursuant to acquisitions, Options	0	0	8
Exercised, Options	(956)	(1,082)	(975)
Forfeited, Options	(10)	(28)	(36)
Outstanding, end of year, Options	2,170	3,136	3,986
Vested and Exercisable, end of year, Options	1,930	2,762	3,539
Outstanding, Weighted-Average Remaining Contractual Term (in years)	4 years 1 month 6 days	4 years 7 months 14 days	4 years 10 months 5 days
Vested and Exercisable, Weighted-Average Remaining Contractual Term (in years)	3 years 6 months 26 days	4 years 15 days	4 years 6 months 12 days
Outstanding, Aggregate Intrinsic Value	$ 191,895	$ 113,822	$ 165,131
Vested and Exercisable, Aggregate Intrinsic Value	$ 178,456	$ 112,379	$ 156,487

Stock-Based Compensation (Stock

Stock-Based Compensation (Stock-Based Compensation Expense) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 53,154	$ 33,347	$ 33,951
Stock-based compensation expense	53,154	33,347	33,951
Related income tax benefits	(20,503)	(10,538)	(11,656)
Stock-based compensation expense, net of taxes	$ 32,651	$ 22,809	$ 22,295
Basic earnings per share	$ (0.38)	$ (0.26)	$ (0.25)
Diluted earnings per share	$ (0.38)	$ (0.26)	$ (0.24)
Software Licenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 969	$ 701	$ 745
Maintenance And Service [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	2,533	1,578	1,868
Selling, General And Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	30,817	15,990	17,153
Research And Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 18,835	$ 15,078	$ 14,185

Stock-Based Compensation (Assum

Stock-Based Compensation (Assumptions To Estimate Fair Value Of Stock Awards) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016$ / shares	Dec. 31, 2015$ / shares
Stock Option Compensation Expense [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Risk-free interest rate, minimum	0.00%	1.19%	1.18%
Risk-free interest rate, maximum	0.00%	1.93%	1.65%
Expected dividend yield		0.00%	0.00%
Expected volatility		24.00%	25.00%
Expected term (in years)		5 years 8 months 7 days	5 years 7 months 7 days
Weighted-average fair value per share		$ 23.96	$ 30.83
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	1.50%	1.00%	1.10%
Correlation factor	0.70	0.65	0.60
Restricted Stock Unit Compensation Expense [Member] | ANSYS Stock Price [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility	19.00%	21.00%	23.00%
Restricted Stock Unit Compensation Expense [Member] | NASDAQ Composite Index [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility	15.00%	16.00%	14.00%

Stock-Based Compensation (Infor

Stock-Based Compensation (Information Regarding Stock Options Outstanding) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2017$ / sharesshares
$5.91 - $40.89
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	$ 40.89
Options Outstanding, Options | shares	437
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	1 year 8 months 27 days
Options Outstanding, Weighted-Average Exercise Price	$ 32.01
Options Exercisable, Options | shares	434
Options Exercisable, Weighted-Average Exercise Price	$ 32.15
$48.97 - $55.30
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	48.97
Range of Exercise Prices, Upper Limit	$ 55.30
Options Outstanding, Options | shares	392
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	2 years 9 months 20 days
Options Outstanding, Weighted-Average Exercise Price	$ 49.11
Options Exercisable, Options | shares	392
Options Exercisable, Weighted-Average Exercise Price	$ 49.11
$ 58.67
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	58.67
Range of Exercise Prices, Upper Limit	$ 58.67
Options Outstanding, Options | shares	492
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	3 years 9 months 36 days
Options Outstanding, Weighted-Average Exercise Price	$ 58.67
Options Exercisable, Options | shares	492
Options Exercisable, Weighted-Average Exercise Price	$ 58.67
$61.68 - $95.09
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	61.68
Range of Exercise Prices, Upper Limit	$ 95.09
Options Outstanding, Options | shares	849
Options Outstanding, Weighted-Average Remaining Contractual Life (years)	6 years 18 days
Options Outstanding, Weighted-Average Exercise Price	$ 78.06
Options Exercisable, Options | shares	612
Options Exercisable, Weighted-Average Exercise Price	$ 72.35

Stock Repurchase Program - Addi

Stock Repurchase Program - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 16, 2018
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased	2,750,000	3,700,000	3,833,000
Average price paid per share	$ 122.20	$ 90.90	$ 88.16
Total cost	$ 336,042	$ 336,335	$ 337,910
Remaining number of shares authorized to be repurchased under stock repurchase program	2,750,000
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 (D

Employee Stock Purchase Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized	39,800,000
Stock-based compensation expense	$ 53,154	$ 33,347	$ 33,951
Employee Stock | ANSYS 1996 Employee Stock Purchase Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized	1,800,000
Share-based compensation arrangement by share-based payment award, expiration period	6 months
Share-based compensation arrangement by share-based payment award, maximum employee subscription rate	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	1,500,000
Stock-based compensation expense	$ 1,200	$ 1,200	$ 1,000
Maximum [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, expiration period	10 years
Maximum [Member] | Employee Stock | ANSYS 1996 Employee Stock Purchase Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Eligibility, ownership percentage of voting power of all classes of stock of the company	5.00%
Purchase price of common stock, percent	90.00%

Leases (Details)

Leases (Details) ft² in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)ft²	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Operating Leased Assets [Line Items]
Lease rental expense incurred	$ 17,100	$ 16,900	$ 16,500
Future minimum lease payments	65,113
Future minimum lease payments, Year 1	14,139
Future minimum lease payments, Year 2	11,570
Future minimum lease payments, Year 3	8,785
Future minimum lease payments, Year 4	7,675
Future minimum lease payments, Year 5	7,046
Future minimum lease payments, Thereafter	$ 15,898
Lease Agreement Effective September 14, 2012 | Canonsburg Office, New Company Headquarters
Operating Leased Assets [Line Items]
Area of real estate property | ft²	186
Period of leased property	183 months
Base rent, years one through five	$ 4,300
Base rent, years six through ten	4,500
Base rent, years eleven through fifteen	4,700
Lease rental expense incurred	$ 4,400	$ 4,400	$ 4,400

Royalty Agreements (Details)

Royalty Agreements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Royalty Agreements [Abstract]
Royalty fees reported in cost of goods sold	$ 16	$ 13.1	$ 11.8

Revenue by Geographic Area (Det

Revenue by Geographic Area (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 1,095,250	$ 988,465	$ 942,753
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	417,342	367,937	354,433
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	126,262	120,160	104,299
Germany
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	108,216	99,814	94,546
South Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	63,011	56,790	55,142
France
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	53,672	49,294	49,444
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	13,824	13,284	13,314
Other European
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	153,826	139,813	145,985
Other international
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 159,097	$ 141,373	$ 125,590

Property and Equipment by Geogr

Property and Equipment by Geographic Area (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	$ 57,096	$ 54,677
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	45,498	43,810
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	5,059	4,753
India
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	3,704	3,033
Other international
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property and equipment, net	$ 2,835	$ 3,081

Unconditional Purchase Obliga76

Unconditional Purchase Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unconditional Purchase Obligations (Excluding Capital Stock Redemptions) [Abstract]
Unconditional purchase obligations, beginning of year	$ 14,100	$ 7,200	$ 5,300
Future expenditures under purchase obligations, next twelve months	22,408
Future expenditures under purchase obligations, year two	18,271
Future expenditures under purchase obligations, year three	6,706
Future expenditures under purchase obligations, year four	4,545
Future expenditures under purchase obligations, year five	0
Future expenditures under purchase obligations	$ 51,930

Restructuring (Details)

Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended	15 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 331	$ 1,435	$ 6,176	$ 2,355		$ 10,297
Payments for restructuring					$ 12,500
Restructuring reserve					$ 2,200	2,200
Operating Income (Loss) [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 466	$ 2,000	$ 9,273	$ 3,419		$ 15,158

Contingencies and Commitments -

Contingencies and Commitments - Additional Information (Detail) $ in Millions	Dec. 31, 2017USD ($)
Maximum [Member]
Other Commitments And Contingencies [Line Items]
Tax charges and related liabilities if the ruling is unfavorable	$ 7.5

Schedule II - Valuation and Q79

Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Provisions for doubtful accounts	$ 1,474	$ 2,009	$ 1,304
Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	5,700	5,200	5,500
Provisions for doubtful accounts	1,474	2,009	1,304
Deductions - returns and write-offs	374	1,509	1,604
Balance at end of year	$ 6,800	$ 5,700	$ 5,200