Accumulated Other Comprehensive Income - Components of and Reclassifications from Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 195,974	$ 207,163
Net change in other comprehensive income, net of tax	0	(544)
Ending balance	184,502	184,502
Accumulated other comprehensive income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	0	544
Ending balance	0	0
Unrealized loss reclassified and recognized in net loss, net of tax
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amount reclassified and recognized in net income or loss, net of tax	0	16
Unrealized gain reclassified to accumulated deficit, net of tax
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amount reclassified and recognized in net income or loss, net of tax	0	(560)
Foreign exchange reclassified and recognized in net loss, net of tax
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amount reclassified and recognized in net income or loss, net of tax	$ 0	$ 0