CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ (DEFICIT) EQUITY (UNAUDITED) - 3 months ended Mar. 31, 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)	26	26
Exercise of common stock options	$ 108		108
Exercise of common stock warrants (in shares)		297
Stock-based compensation	2,906		2,906
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 loss	(508)			(508)
Net loss	(20,055)				(20,055)
Ending balance (in shares) at Mar. 31, 2018		20,226
Ending balance at Mar. 31, 2018	$ 40,558	$ 7	$ 328,493	$ 558	$ (288,500)