Fair Value Measurements (Fair Value for Level 3 Liabilities) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 47,285	$ 51,826
Contingent consideration recorded at acquisition date	11,669	15
Payment of contingent consideration recorded at acquisition date	(4,976)	(5,565)
Payment of contingent consideration recorded in earnings	(11)
Adjustments to contingent consideration	349	11,013
Interest accretion expense	852	1,026
Ending balance	54,988	$ 58,315
Foreign Currency Translation Adjustment [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Foreign currency translation adjustment	$ (180)