Description of Operations and Summary of Significant Accounting Policies - Summary of Select Unaudited Condensed Consolidated Statement of Cash Flows Reflect Adoption of Accounting Standards (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities
Net loss	$ (5,297)	$ (6,912)		$ (13,396)	$ (14,051)
Adjustments to reconcile net loss to net cash provided by operating activities:
Amortization of deferred costs				7,950	6,616	[1]
Foreign exchange loss (gain)				462	(66)	[1]
Change in operating assets and liabilities
Deferred costs				(8,163)	(6,119)	[1]
Net cash provided by operating activities				8,132	1,743	[1]
Foreign currency effect on cash, cash equivalents and restricted cash				(353)	56	[1]
Net decrease in cash, cash equivalents and restricted cash				119,925	(2,173)	[1]
Cash, cash equivalents and restricted cash
End of period	$ 174,994	39,834	[1]	$ 174,994	39,834	[1]
ASU 2014-09 | As Previously Reported
Cash flows from operating activities
Net loss		(7,013)			(13,560)
Adjustments to reconcile net loss to net cash provided by operating activities:
Foreign exchange loss (gain)					(68)
Change in operating assets and liabilities
Net cash provided by operating activities					1,735
Foreign currency effect on cash, cash equivalents and restricted cash					64
Net decrease in cash, cash equivalents and restricted cash					(2,173)
Cash, cash equivalents and restricted cash
End of period		39,834			39,834
ASU 2014-09 | Adjustments
Cash flows from operating activities
Net loss		$ 101			(491)
Adjustments to reconcile net loss to net cash provided by operating activities:
Amortization of deferred costs					6,616
Foreign exchange loss (gain)					2
Change in operating assets and liabilities
Deferred costs					(6,119)
Net cash provided by operating activities					8
Foreign currency effect on cash, cash equivalents and restricted cash					$ (8)

[1] See Note 1 for a summary of adjustments