Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Fair value of assets and liabilities measured on recurring basis
Short-term investments		$ 133,848	$ 98,341
Summary of changes in fair value of the Company's Level 3 contingent consideration payments
Payment of contingent acquisition related obligations		40,000
Change in contingent acquisition-related obligations	17,800	17,813
Fair value measurements recurring basis | Quoted prices for identical instruments in active markets (Level 1)
Fair value of assets and liabilities measured on recurring basis
Short-term investments		133,848	98,341
Total		133,848	98,341
Fair value measurements recurring basis | Significant Observable Inputs (Level 2)
Fair value of assets and liabilities measured on recurring basis
Forward contracts		5,105
Total		5,105
Fair value measurements recurring basis | Significant unobservable inputs (Level 3)
Fair value of assets and liabilities measured on recurring basis
Contingent consideration payments			56,668
Total		0	56,668
Summary of changes in fair value of the Company's Level 3 contingent consideration payments
Balance at the beginning of the period		56,668
Accretion of discount on contingent consideration liabilities		1,145
Payment of contingent acquisition related obligations		(40,000)
Change in contingent acquisition-related obligations		(17,813)
Fair value measurements recurring basis | Total
Fair value of assets and liabilities measured on recurring basis
Short-term investments		133,848	98,341
Forward contracts		5,105
Contingent consideration payments			56,668
Total		$ 138,953	$ 155,009