Revision of Prior Period Financial Statements - Schedule of Revised Consolidated Statements of Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss	$ (17,300)	$ (18,293)	$ (10,725)	$ (8,250)	$ (16,270)	$ (9,727)	$ (13,304)	$ (11,077)	$ (54,568)	$ (50,378)	$ (29,740)
Net change in unrealized gains on available-for-sale securities									98	49	(56)
Comprehensive loss									$ (54,470)	(50,329)	(29,796)
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss			(11,467)	(8,019)	(14,713)		(12,206)	(11,117)		(48,280)	(29,420)
Net change in unrealized gains on available-for-sale securities										24
Comprehensive loss										(48,256)	(29,476)
Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss			$ 742	$ (231)	$ (1,557)		$ (1,098)	$ 40		(2,098)	(320)
Net change in unrealized gains on available-for-sale securities										25
Comprehensive loss										$ (2,073)	$ (320)