Subsidiary Merger Activities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Dec. 31, 2010
Extraordinary and Unusual Items [Abstract]
Taxable gain from mergers	$ 77.3
Reduction in tax payments	22.4
Refund of foreign tax credit	$ 26.3

Reduction In Prior Period US Tax Payments Due To Foreign Merger Tax Credit

No definition available.

Name:	anss_ReductionInPriorPeriodUsTaxPaymentsDueToForeignMergerTaxCredit
Namespace Prefix:	anss_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant