Other Comprehensive Income (Loss) - Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), balance at beginning of period, net	$ 882	$ 781
Foreign currency translation adjustments	(1,343)	1,027
Other comprehensive income (loss) before reclassifications	(407)	6,146
Amounts reclassified from accumulated other comprehensive income (loss)	(6)	(7,072)
Accumulated other comprehensive income (loss), balance at end of period, net	(874)	882
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), balance at beginning of period, net	1,027
Foreign currency translation adjustments	(1,343)	1,027
Accumulated other comprehensive income (loss), balance at end of period, net	(316)	1,027
Unrealized/Recognized Gains (Losses)
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), balance at beginning of period, net	(145)	781
Other comprehensive income (loss) before reclassifications	(407)	6,146
Amounts reclassified from accumulated other comprehensive income (loss)	(6)	(7,072)
Accumulated other comprehensive income (loss), balance at end of period, net	$ (558)	$ (145)