Statements of Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional paid-in capital	Accumulated deficit	Total
Stockholders' (deficit) equity beginning balance at Dec. 31, 2018	$ 333	$ 254,516	$ (105,538)	$ 149,311
Stockholders' (deficit) equity shares beginning balance at Dec. 31, 2018	33,341
Stockholders' (Deficit) Equity Rollforward
Issuance of common stock upon vesting of restricted stock awards	$ 1	(1)
Issuance of common stock upon vesting of restricted stock awards (in shares)	70
Stock-based compensation		2,000		2,000
Issuance of common stock upon exercise of stock options		86		86
Issuance of common stock upon exercise of stock options (in shares)	26
Net loss			(16,711)	(16,711)
Stockholders' (deficit) equity ending balance at Mar. 31, 2019	$ 334	256,601	(122,249)	134,686
Stockholders' (deficit) equity shares ending balance at Mar. 31, 2019	33,437
Stockholders' (deficit) equity beginning balance at Dec. 31, 2019	$ 337	263,922	(162,948)	$ 101,311
Stockholders' (deficit) equity shares beginning balance at Dec. 31, 2019	33,739			45,546
Stockholders' (Deficit) Equity Rollforward
Issuance of common stock upon vesting of restricted stock awards (in shares)	11
Stock-based compensation		2,331		$ 2,331
Issuance of common stock upon public offering, net of underwriters’ discount and other offering costs of $1,733	$ 117	33,225		33,342
Issuance of common stock upon public offering, net of underwriters’ discount and other offering costs of $1,733 (in shares)	11,692
Issuance of common stock upon exercise of stock options	$ 1	243		244
Issuance of common stock upon exercise of stock options (in shares)	104
Net loss			(14,710)	(14,710)
Stockholders' (deficit) equity ending balance at Mar. 31, 2020	$ 455	$ 299,721	$ (177,658)	$ 122,518
Stockholders' (deficit) equity shares ending balance at Mar. 31, 2020	45,546			45,546