Deferred Acquisition Consideration (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Payments			$ 24,492
Redemption value adjustments	$ 734	$ (2,744)	(6,100)
Additions			5,695
Foreign translation adjustment			0
Ending balance of contingent payments	57,701		57,701
Deferred acquisition consideration	58,243		58,243
Stock-based compensation	(1,339)	2,321	(530)	$ 4,682
Fixed payments
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Deferred acquisition consideration	542		542
Contingent Payment
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Income (loss) attributable to fair value adjustments	$ 2,073	$ (5,065)	$ (5,570)	$ (2,479)