Acquisitions (Recognized Amounts Of Identifiable Assets Acquired And Liabilities) (Details) (Apache Design Solutions, Inc [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2011 years
Business Acquisition [Line Items]
Cash and short term investments	$ 31,948
Accounts receivable and other tangible assets	6,011
Accounts payable and other liabilities	(16,563)
Deferred revenue	(10,100)
Net deferred tax liabilities	(46,138)
Total identifiable net assets	118,958
Goodwill	195,286
Developed Software [Member]
Business Acquisition [Line Items]
Amortizable intangible assets	81,900
Useful life of intangible assets acquired, in years	7
Customer Relationships [Member]
Business Acquisition [Line Items]
Amortizable intangible assets	37,500
Useful life of intangible assets acquired, in years	20
Contract Backlog [Member]
Business Acquisition [Line Items]
Amortizable intangible assets	12,800
Useful life of intangible assets acquired, in years	3
Platform Trade names [Member]
Business Acquisition [Line Items]
Indefinite-lived intangible assets	19,500
Apache Trade Name [Member]
Business Acquisition [Line Items]
Amortizable intangible assets	$ 2,100
Useful life of intangible assets acquired, in years	6