Basis of Presentation and Summary of Significant Accounting Policies - Condensed Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Net loss	$ (17,820)	$ (14,762)
Adjustments to reconcile net loss to net cash used in operating activities:
Deferred revenue	(5,331)	(2,410)
Cash, cash equivalents and restricted cash, beginning of period	224,857	136,056
Cash, cash equivalents and restricted cash, end of period	$ 184,151	135,853
As Originally Reported | Accounting Standards Update 2014-09
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Net loss		(11,547)
Adjustments to reconcile net loss to net cash used in operating activities:
Deferred revenue		(5,625)
Cash, cash equivalents and restricted cash, beginning of period		135,797
Cash, cash equivalents and restricted cash, end of period		135,594
Effect of Change | Accounting Standards Update 2014-09
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Net loss		(3,215)
Adjustments to reconcile net loss to net cash used in operating activities:
Deferred revenue		3,215
Cash, cash equivalents and restricted cash, beginning of period		259
Cash, cash equivalents and restricted cash, end of period		$ 259