Revenue Information by Products and Services (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2011	Oct. 31, 2010	Oct. 31, 2011	Oct. 31, 2010
Revenues:
Total revenues	$ 250,508	$ 238,937	$ 694,283	$ 607,448
IC Design To Silicon
Revenues:
Total revenues	96,478	83,433	236,400	226,157
Integrated System Design
Revenues:
Total revenues	60,087	57,839	168,933	152,352
Scalable Verification
Revenues:
Total revenues	65,146	67,088	185,948	143,453
New & Emerging Products
Revenues:
Total revenues	11,895	14,877	53,479	40,001
Services & Other
Revenues:
Total revenues	$ 16,902	$ 15,700	$ 49,523	$ 45,485