Intangible Assets, Net (Details) (USD $)	3 Months Ended		6 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2011	Jul. 31, 2010	Jan. 31, 2011
Intangible assets, Gross carrying amount	$ 426,436,000		$ 426,436,000		$ 419,398,000
Intangible assets, Accumulated amortization	249,108,000		249,108,000		222,938,000
Intangible assets, net	177,328,000		177,328,000		196,460,000
Amortization of intangible assets	12,600,000	12,200,000	25,300,000	24,400,000
Impairment of finite-lived intangible assets	0	0	0	0
Acquired Technology [Member]
Intangible assets, Gross carrying amount	167,330,000		167,330,000		164,796,000
Intangible assets, Accumulated amortization	123,519,000		123,519,000		110,740,000
Intangible assets, Useful Life, Minimum, Years			2
Intangible assets, Useful Life, Maximum, Years			7
Customer Relationships [Member]
Intangible assets, Gross carrying amount	237,007,000		237,007,000		233,995,000
Intangible assets, Accumulated amortization	108,090,000		108,090,000		95,753,000
Intangible assets, Useful Life, Minimum, Years			4
Intangible assets, Useful Life, Maximum, Years			10
Trade Names [Member]
Intangible assets, Gross carrying amount	13,007,000		13,007,000		12,952,000
Intangible assets, Accumulated amortization	13,007,000		13,007,000		12,577,000
Intangible assets, Useful Life, Minimum, Years			1
Intangible assets, Useful Life, Maximum, Years			10
Non-Competition Agreements [Member]
Intangible assets, Gross carrying amount	5,809,000		5,809,000		5,215,000
Intangible assets, Accumulated amortization	3,262,000		3,262,000		2,760,000
Intangible assets, Useful Life, Minimum, Years			4
Intangible assets, Useful Life, Maximum, Years			10
Sales Backlog [Member]
Intangible assets, Gross carrying amount	843,000		843,000
Intangible assets, Useful Life, Years			3
Distribution Network [Member]
Intangible assets, Gross carrying amount	2,440,000		2,440,000		2,440,000
Intangible assets, Accumulated amortization	$ 1,230,000		$ 1,230,000		$ 1,108,000
Intangible assets, Useful Life, Years			10