Income Taxes - Components of net deferred tax liability (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Components of Deferred Tax Assets and Liabilities [Abstract]
Accrued expenses	$ 3,042	$ 2,356
Stock Compensation	2,164	0
Foreign tax credits	13,571	11,454
Net operating loss carryforwards	43,637	42,205
Research and development credits	4,530	3,320
Other	4,492	4,113
Total deferred tax assets	71,436	63,448
Valuation allowance	(40,857)	(33,774)
Deferred tax assets, net of valuation allowance	30,579	29,674
Deferred tax liabilities:
Prepaid expenses and other	(511)	(359)
Intangible assets	19,552	25,493
Property and equipment, net	(9,415)	(3,723)
Deferred tax liabilities	(29,478)	(29,575)
Net deferred tax assets	$ 1,101	$ 99