CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ (DEFICIT) EQUITY (UNAUDITED) - 6 months ended Jun. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017		3,439
Beginning balance at Dec. 31, 2017	$ (208,686)	$ 0	$ 58,693	$ 1,066	$ (268,445)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)	64	64
Exercise of common stock options	$ 144		144
Exercise of common stock warrants (in shares)		349
Stock-based compensation	11,251		11,251
Issuance of common stock in connection with our IPO (in shares)		5,821
Issuance of common stock in connection with our IPO	66,101	$ 1	66,100
Vesting of performance-based common stock warrants	2,519		2,519
Conversion of preferred stock to common stock (in shares)		10,643
Conversion of preferred stock to common stock	196,594	$ 6	196,588
Conversion of preferred stock warrants to common stock warrants	1,736		1,736
Accretion of redeemable convertible preferred stock to redemption value	(157)		(157)
Other comprehensive income	372			372
Net loss	(33,108)				(33,108)
Ending balance (in shares) at Jun. 30, 2018		20,316
Ending balance at Jun. 30, 2018	$ 36,766	$ 7	$ 336,874	$ 1,438	$ (301,553)