Income Taxes - Reconciliation of Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory tax rate	12.50%	12.50%	12.50%	12.50%
International tax rates differential	10.60%	(1.50%)	6.90%	6.80%
Change in valuation allowance	(52.90%)	(39.40%)	(25.40%)	(11.90%)
Change in fair value of nondeductible contingent consideration	1.60%	67.60%	(1.50%)	10.90%
Nondeductible stock-based compensation	0.00%	(4.70%)	(0.20%)	(1.80%)
Unrecognized tax benefits	(2.50%)	(7.60%)	(1.40%)	(2.80%)
State and local income taxes, net of federal	(0.40%)	1.00%	(0.10%)	0.30%
Nondeductible interest expense	(3.70%)	0.00%	(2.00%)	0.00%
Other	8.70%	(18.90%)	4.40%	0.50%
Effective income tax rate	(26.10%)	9.00%	(6.80%)	14.50%
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax benefit - at statutory tax rate	$ (853)	$ (473)	$ (2,526)	$ (2,293)
International tax rates differential	(723)	57	(1,391)	(1,241)
Change in valuation allowance	3,609	1,491	5,129	2,181
Change in fair value of nondeductible contingent consideration	(110)	(2,556)	303	(2,005)
Nondeductible stock-based compensation	(2)	176	49	336
Unrecognized tax benefits	168	288	292	508
State and local income taxes, net of federal	25	(38)	27	(57)
Nondeductible interest expense	253	0	410	0
Other	(586)	713	(886)	(98)
Income tax provision (benefit) - at effective income tax rate	$ 1,781	$ (342)	$ 1,407	$ (2,669)