Fair Value Measurement (Reconciliation of Level 3 Liabilities) (Details) (Level 3, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Level 3
Reconciliation of beginning and ending Level 3 financial liability balance
Beginning balance	$ 3,015	$ 2,977	$ 2,705
Earnouts related to acquisition	17,733	2,581	0
Payment of contingent purchase obligation	(284)	(3,212)	0
Adjustment to contingent purchase obligation	443	669	272
Ending balance	$ 20,907	$ 3,015	$ 2,977