Acquisition - Additional Information (Detail) (USD $)	12 Months Ended			12 Months Ended	0 Months Ended	12 Months Ended		5 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Aug. 01, 2011	Dec. 31, 2012 Apache Performance Restricted Stock Units	Aug. 01, 2012 Apache Design Solutions, Inc.	Dec. 31, 2012 Apache Design Solutions, Inc.	Aug. 01, 2011 Apache Design Solutions, Inc.	Dec. 31, 2012 Esterel Technologies, S.A.	Dec. 31, 2012 Esterel Technologies, S.A.	Aug. 01, 2012 Esterel Technologies, S.A.
Business Acquisition [Line Items]
Business acquisition, acquisition percentage							100.00%			100.00%
Business acquisition, purchase price							$ 313,977,000			$ 58,200,000
Business acquisition, cash on subsidiary balance sheet							31,948,000			13,075,000
Business Acquisition, Pro Forma Revenue								3,297,000
Business Acquisition, Pro Forma Net Income (Loss)								(3,833,000)
Business Combination, Acquisition Related Costs									906,000
Acquired deferred revenue							10,100,000			1,139,000
Acquired deferred revenue, amount lower than the historical carrying value recorded on the opening balance sheet						13,600,000				(10,973,000)
Acquired deferred revenue, impact on reported revenue						3,400,000			6,202,000
Acquired deferred revenue, expected impact on reported revenue in next quarter						0		1,632,000	1,632,000
Acquired deferred revenue, expected impact on reported revenue in next fiscal year						497,000		4,104,000	4,104,000
ANSYS replacement stock options							3,170,000
Contingent consideration							(9,501,000)
Contingent consideration arrangement, additional payments							12,000,000
Contingent payments					4,000,000
Business acquisition, potential performance equity awards						13,000,000
Business acquisition performance equity awards service period	3 years
Value of each restricted stock unit on grant date				$ 50.30
Stock-based compensation expense				3,900,000
Net deferred tax liabilities			(46,100,000)				(47,229,000)			(9,286,000)
Amortizable intangible assets			153,800,000				156,100,000
Reduction in purchase price								1,320,000	1,320,000
Reduction in goodwill due to reduction in purchased price									$ 1,300,000
Business combination, goodwill recognized, description	The goodwill, which is not tax-deductible, is attributed to intangible assets that do not qualify for separate recognition, including the assembled workforce of the acquired business and the synergies expected to arise as a result of the acquisition of Esterel.	The goodwill, which is not tax-deductible, is attributed to intangible assets that do not qualify for separate recognition, including the assembled workforce of the acquired business and the synergies expected to arise as a result of the acquisition of Apache.
Nature of preliminary adjustments		These adjustments were based on refinements to assumptions used in the preliminary valuation of intangible assets and information about what was known and knowable as of the acquisition date in the calculation of the net deferred tax liabilities.