Fair Value Measurements Fair Value Measurements (Change in contingent consideration) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 2,047	$ 2,945
Change in fair value	(643)	(898)	$ 41
Payments	0	0
Ending Balance	$ 1,404	$ 2,047	$ 2,945