Acquisition (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Jan. 31, 2012
Assets acquired and liabilities assumed are recorded at their fair values as of the acquisition date
Tangible assets acquired		$ 21,666
Liabilities assumed		15,898
Identifiable net assets acquired		5,768
Fair value adjustments to intangible assets
Fair value of intangible assets acquired		150,699
Purchase price:
Cash paid	287,500	287,500
Less identifiable net assets acquired		(5,768)
Plus deferred tax liability related to intangible assets		55,132
Less fair value of intangible assets acquired		(150,699)
Excess of purchase price over net assets acquired, allocated to goodwill		186,165
Customer relationships [Member]
Fair value adjustments to intangible assets
Fair value of intangible assets acquired		101,400
Purchase price:
Less fair value of intangible assets acquired		(101,400)
Proprietary technology [Member]
Fair value adjustments to intangible assets
Fair value of intangible assets acquired		29,800
Purchase price:
Less fair value of intangible assets acquired		(29,800)
Trade name [Member]
Fair value adjustments to intangible assets
Fair value of intangible assets acquired		19,499
Purchase price:
Less fair value of intangible assets acquired		$ (19,499)