Acquisitions (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	7 Months Ended
	Jun. 30, 2011 years	Jul. 31, 2011 Apache Design Solutions, Inc [Member]
Business acquisition, purchase price		$ 314.0
Business acquisition, cash on subsidiary balance sheet		31.0
Business Acquisition, contingent consideration, at fair value		12
Business acquisition, potential performance equity awards		$ 13.0
Business acquisition, acquisition percentage	100.00%
Business acquisition, incentive and provision fiscal period (in years)	3