Intangible Assets, Net (Details) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2011	Oct. 31, 2010	Oct. 31, 2011	Oct. 31, 2010	Jan. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross carrying amount	$ 478,336,000		$ 478,336,000		$ 419,398,000
Intangible assets, Accumulated amortization	262,019,000		262,019,000		222,938,000
Intangible assets, net	216,317,000		216,317,000		196,460,000
Amortization of intangible assets	13,600,000	12,300,000	38,900,000	36,700,000
Impairment of finite-lived intangible assets	0	0	0	0
Acquired Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross carrying amount	190,272,000		190,272,000		164,796,000
Intangible assets, Accumulated amortization	130,130,000		130,130,000		110,740,000
Intangible assets, Useful Life, Minimum, Years			2
Intangible assets, Useful Life, Maximum, Years			7
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross carrying amount	263,001,000		263,001,000		233,995,000
Intangible assets, Accumulated amortization	114,029,000		114,029,000		95,753,000
Intangible assets, Useful Life, Minimum, Years			4
Intangible assets, Useful Life, Maximum, Years			10
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross carrying amount	15,983,000		15,983,000		12,952,000
Intangible assets, Accumulated amortization	13,102,000		13,102,000		12,577,000
Intangible assets, Useful Life, Minimum, Years			1
Intangible assets, Useful Life, Maximum, Years			10
Non-Competition Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross carrying amount	5,797,000		5,797,000		5,215,000
Intangible assets, Accumulated amortization	3,462,000		3,462,000		2,760,000
Intangible assets, Useful Life, Minimum, Years			4
Intangible assets, Useful Life, Maximum, Years			10
Sales Backlog [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross carrying amount	843,000		843,000
Intangible assets, Accumulated amortization	5,000		5,000
Intangible assets, Useful Life, Years			3
Distribution Network [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross carrying amount	2,440,000		2,440,000		2,440,000
Intangible assets, Accumulated amortization	$ 1,291,000		$ 1,291,000		$ 1,108,000
Intangible assets, Useful Life, Years			10