Goodwill and Intangible Assets (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Estimated future amortization expense
Amortization expense for 2013	$ 15,200
Amortization expense for 2014	13,700
Amortization expense for 2015	8,400
Amortization expense for 2016	5,400
Amortization expense for 2017	2,500
Increase in goodwill resulting from acquisitions	7,600	4,700
Foreign currency translation adjustment	$ 5,200	$ 13,500