Revenue Information by Products and Services (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 30, 2012	Apr. 30, 2011
Revenues:
Total revenues	$ 247,918	$ 230,035
IC Design to Silicon
Revenues:
Total revenues	103,189	86,288
Integrated System Design
Revenues:
Total revenues	55,676	51,609
Scalable Verification
Revenues:
Total revenues	56,310	58,742
New & Emerging Products
Revenues:
Total revenues	15,405	17,968
Services & Other
Revenues:
Total revenues	$ 17,338	$ 15,428