Other Comprehensive Income (Loss) - Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), balance at beginning of period, net		$ 781
Foreign currency translation adjustments	$ 232	1,078
Other comprehensive income (loss) before reclassifications		4,716
Amounts reclassified from accumulated other comprehensive income (loss)		(401)
Accumulated other comprehensive income (loss), balance at end of period, net	6,174	6,174
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Foreign currency translation adjustments		1,078
Accumulated other comprehensive income (loss), balance at end of period, net	1,078	1,078
Unrealized/Recognized Gains (Losses)
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), balance at beginning of period, net		781
Other comprehensive income (loss) before reclassifications		4,716
Amounts reclassified from accumulated other comprehensive income (loss)		(401)
Accumulated other comprehensive income (loss), balance at end of period, net	$ 5,096	$ 5,096