Other Long-Term Liabilities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Other Liabilities Disclosure [Abstract]
Uncertain tax positions	$ 37.0	$ 35.5

Unrecognized Tax Benefits Accrued Including Income Tax Penalties And Interest

No definition available.

Name:	anss_UnrecognizedTaxBenefitsAccruedIncludingIncomeTaxPenaltiesAndInterest
Namespace Prefix:	anss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant