Revenue Information by Products and Services (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010
Revenues:
Total revenues	$ 1,014,638	$ 914,753	$ 802,727
IC Design To Silicon
Revenues:
Total revenues	382,935	314,904	330,575
Integrated System Design
Revenues:
Total revenues	234,112	245,997	193,202
Scalable Verification
Revenues:
Total revenues	268,369	227,069	180,599
New & Emerging Products
Revenues:
Total revenues	74,104	64,693	48,863
Services & Other
Revenues:
Total revenues	$ 55,118	$ 62,090	$ 49,488