Income Taxes - Income tax (benefit) expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ (773)	$ (250)	$ (958)
State	227	47	113
Foreign	(6,830)	5,365	5,865
Total current income tax (benefit) expense	(7,376)	5,162	5,020
Deferred:
Federal	379	(5,497)	(7,550)
State	48	(372)	(31)
Foreign	(1,428)	(1,182)	(439)
Deferred Income Tax Expense (Benefit)	(1,001)	(7,051)	(8,020)
Income tax (benefit) expense	$ (8,377)	$ (1,889)	$ (3,000)