Revenue Information by Products and Services (Detail) (USD $) In Thousands	3 Months Ended				6 Months Ended
	Jul. 31, 2011	Apr. 30, 2011	Jul. 31, 2010	Apr. 30, 2010	Jul. 31, 2011	Jul. 31, 2010
Revenues:
Total revenues	$ 213,740	$ 230,035	$ 187,934	$ 180,577	$ 443,775	$ 368,511
IC Design To Silicon
Revenues:
Total revenues	53,633		71,192		139,921	142,724
Integrated System Design
Revenues:
Total revenues	57,300		49,922		108,845	94,513
Scalable Verification
Revenues:
Total revenues	62,060		39,629		120,802	76,366
New & Emerging Products
Revenues:
Total revenues	23,616		11,797		41,584	25,125
Services & Other
Revenues:
Total revenues	$ 17,131		$ 15,394		$ 32,623	$ 29,783