Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Financial assets measured at fair value on a recurring basis
Cash equivalents (money market accounts and commercial paper investments)	51,995	111,775
Hedges of interest rate risk	(88)	(36)
Acquisition contingent consideration obligations	(461)	(1,197)
Fair value assets and liabilities measured on recurring basis, net	51,446	110,542
Hedges of interest rate risk [Member]
Valuation technique (approach)
Valuation Technique (Approach)	Market	Market
Acquisition contingent consideration obligations [Member]
Valuation technique (approach)
Valuation Technique (Approach)	Income	Income
Cash equivalents (money market accounts and commercial paper investments) [Member]
Valuation technique (approach)
Valuation Technique (Approach)	Market	Market
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Financial assets measured at fair value on a recurring basis
Cash equivalents (money market accounts and commercial paper investments)	51,995	111,775
Fair value assets and liabilities measured on recurring basis, net	51,995	111,775
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Financial assets measured at fair value on a recurring basis
Hedges of interest rate risk	(88)	(36)
Fair value assets and liabilities measured on recurring basis, net	(88)	(36)
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Financial assets measured at fair value on a recurring basis
Acquisition contingent consideration obligations	(461)	(1,197)
Fair value assets and liabilities measured on recurring basis, net	(461)	(1,197)