Income Taxes - Reconciliation of Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory tax rate	12.50%	12.50%	12.50%	12.50%
International tax rates differential	(4.30%)	7.00%	4.10%	6.90%
Change in valuation allowance	(31.10%)	(18.30%)	(27.00%)	(14.90%)
Change in fair value of nondeductible contingent consideration	4.10%	8.70%	(0.10%)	9.90%
Nondeductible stock-based compensation	0.00%	(3.50%)	(0.20%)	(2.60%)
Unrecognized tax benefits	(8.80%)	(3.50%)	(3.30%)	(3.10%)
State and local income taxes, net of federal	(0.20%)	0.10%	(0.20%)	0.20%
Nondeductible interest expense	(4.50%)	0.00%	(2.60%)	0.00%
Other	(1.30%)	1.20%	3.10%	0.80%
Effective income tax rate	(33.60%)	4.20%	(13.70%)	9.70%
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax benefit - at statutory tax rate	$ (829)	$ (2,058)	$ (3,355)	$ (4,351)
International tax rates differential	283	(1,153)	(1,108)	(2,394)
Change in valuation allowance	2,059	3,007	7,242	5,188
Change in fair value of nondeductible contingent consideration	(270)	(1,431)	33	(3,436)
Nondeductible stock-based compensation	1	578	50	914
Unrecognized tax benefits	581	578	873	1,086
State and local income taxes, net of federal	14	(13)	41	(70)
Nondeductible interest expense	299	0	709	0
Other	96	(199)	(844)	(297)
Income tax provision (benefit) - at effective income tax rate	$ 2,234	$ (691)	$ 3,641	$ (3,360)