Income Taxes - Current and deferred expense for income tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Deferred expense (benefit):
Foreign	$ 20	$ (157)
Total deferred expense (benefit):	20	(157)
Total income tax expense (benefit):	$ 20	$ (157)