Income Taxes - Reconciliation of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Tax expense at statutory rate		$ 956	$ 1,981	$ 4,427
Tax expense (benefit), statutory rate		34.00%	34.00%	34.00%
State income taxes, net of federal benefit		$ (195)	$ 81	$ (50)
Foreign tax rate difference		(1,003)	(2,057)	(1,939)
Research and development credit		(919)	(1,037)	(917)
Change in valuation allowance		464	678	162
Equity based compensation		(198)	33	(255)
Manufacturing credit		0	(191)	(61)
Permanent impact of non-deductible cost		1,120	766	412
Provision to return adjustments		345	777	(61)
Impact of Tax Cuts and Jobs Act of 2017		(1,000)	19,355	0
Other		58	(43)	(199)
Income tax (benefit) expense	$ 1,000	$ (372)	$ 20,343	$ 1,519