Acquisitions - Fair Value of Consideration Transferred 2020 (Details) - USD ($) shares in Thousands, $ in Thousands			12 Months Ended
	Dec. 01, 2020	Apr. 01, 2020	Dec. 31, 2021	Dec. 31, 2020
Cash				$ 602,611
Ansys common stock				222,236
Consideration not yet paid				2,787
Total consideration transferred at fair value				827,634
Analytical Graphics, Inc.
Cash	$ 495,066
Ansys common stock	222,236
Consideration not yet paid	2,787
Total consideration transferred at fair value	$ 720,089
Stock issued to prior owners of Analytical Graphics, Inc., amount			$ 3,888	$ 218,348
Analytical Graphics, Inc. | Common Stock
Common stock issued to prior owners of Analytical Graphics, Inc., shares	600		1	638
Stock issued to prior owners of Analytical Graphics, Inc., amount				$ 7
Analytical Graphics, Inc. | Common Stock | Prior AGI Owners
Stock issued to prior owners of Analytical Graphics, Inc., amount	$ 217,700
Analytical Graphics, Inc. | Treasury Stock
Stock issued to prior owners of Analytical Graphics, Inc., amount			$ 819	$ 233
Analytical Graphics, Inc. | Treasury Stock | Prior AGI Owners
Stock issued to prior owners of Analytical Graphics, Inc., amount	$ 4,500
Lumerical
Cash		$ 107,545
Total consideration transferred at fair value		$ 107,545