Accumulated Other Comprehensive Income - Reclassifications from Accumulated Other Comprehensive Income and Included in Earnings (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		$ 207,163	$ 427,569
Amount reclassified and recognized in net income or loss, net of tax	$ (393)	(544)	(6,356)
Net change in other comprehensive income, net of tax	(381)	(544)	(6,254)
Ending balance	323,960	184,502	323,960
Accumulated other comprehensive income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	788	544	6,661
Ending balance	407	0	407
Unrealized (gain) loss reclassified and recognized in net loss, net of tax
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		544
Amount reclassified and recognized in net income or loss, net of tax	(392)	16	(6,357)
Unrealized gain reclassified and recognized in net loss, net of tax	5	0	72
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)	0
Foreign currency translation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		0
Amount reclassified and recognized in net income or loss, net of tax	(1)	0	1
Unrealized gain reclassified and recognized in net loss, net of tax	$ 7	$ 0	$ 30