Annual report pursuant to Section 13 and 15(d)

Fair Value of Assets and Liabilities (Schedule of Changes in Carrying Value of Contingent Consideration) (Details)

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Fair Value of Assets and Liabilities (Schedule of Changes in Carrying Value of Contingent Consideration) (Details) - Contingent Consideration - 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 of contingent consideration $ 7,144 $ 2,813 $ 3,212
Payments (5,021) (827) (1,945)
Change in fair value of contingent consideration (19) 216 (55)
Fair value of contingent consideration in connection with acquisitions   4,942 1,601
Ending balance of contingent consideration $ 2,104 $ 7,144 $ 2,813