Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Total
Balance at Dec. 31, 2016	$ 3	$ 225,889	$ (173,879)	$ (5)	$ 52,008
Balance, shares at Dec. 31, 2016	25,024,100
Stockholders' Equity
Issuance of common stock upon exercise of stock options		685			685
Issuance of common stock upon exercise of stock options, shares	220,520
Issuance of common stock in connection with employee stock purchase plan		276			276
Issuance of common stock in connection with employee stock purchase plan, shares	53,662
Issuance of common stock upon public offering, net of issuance costs		29,238			29,238
Issuance of common stock upon public offering, net of issuance costs, shares	4,359,920
Unrealized gain on marketable securities				$ 5	5
Stock-based compensation expense		7,321			7,321
Net loss			(63,386)		(63,386)
Balance at Dec. 31, 2017	$ 3	263,409	(237,265)		26,147
Balance, shares at Dec. 31, 2017	29,658,202
Stockholders' Equity
Issuance of common stock upon exercise of stock options		397			397
Issuance of common stock upon exercise of stock options, shares	182,261
Issuance of common stock in connection with employee stock purchase plan		297			297
Issuance of common stock in connection with employee stock purchase plan, shares	81,455
Issuance of common stock upon public offering, net of issuance costs	$ 1	61,528			61,529
Issuance of common stock upon public offering, net of issuance costs, shares	11,596,173
Stock-based compensation expense		7,483			7,483
Net loss			(59,978)		(59,978)
Balance at Dec. 31, 2018	$ 4	333,114	(297,243)		35,875
Balance, shares at Dec. 31, 2018	41,518,091
Stockholders' Equity
Issuance of common stock upon exercise of stock options		78			$ 78
Issuance of common stock upon exercise of stock options, shares	28,583				28,583
Issuance of common stock in connection with employee stock purchase plan		451			$ 451
Issuance of common stock in connection with employee stock purchase plan, shares	130,945
Issuance of common stock upon public offering, net of issuance costs	$ 1	37,578			37,579
Issuance of common stock upon public offering, net of issuance costs, shares	8,655,940
Stock-based compensation expense		8,759			8,759
Net loss			(86,372)		(86,372)
Balance at Dec. 31, 2019	$ 5	$ 379,980	$ (383,615)		$ (3,630)
Balance, shares at Dec. 31, 2019	50,333,559