Revenue from Contracts with Customers - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Amounts of revenue recognized from beginning deferred revenue and backlog	$ 569.8	$ 475.9

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

No definition available.

Name:	anss_ContractWithCustomerDeferredRevenueAndBacklogRevenueRecognized
Namespace Prefix:	anss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration