CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance at the beginning of the period (in shares) at Dec. 31, 2018		28,314,274
Balance at the beginning of the period at Dec. 31, 2018	$ 101,249	$ 28	$ 275,058	$ (75)	$ (173,762)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	1,729		1,729
Exercise of stock options (in shares)		17,070
Exercise of stock options	45		45
Vesting of restricted common stock	5		5
Unrealized gains on marketable securities	67			67
Net loss	(21,024)				(21,024)
Balance at the end of the period (in shares) at Mar. 31, 2019		28,331,344
Balance at the end of the period at Mar. 31, 2019	$ 82,071	$ 28	276,837	(8)	(194,786)
Balance at the beginning of the period (in shares) at Dec. 31, 2019	28,729,725	28,729,725
Balance at the beginning of the period at Dec. 31, 2019	$ 29,417	$ 29	282,926	0	(253,538)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	1,669		1,669
Vesting of restricted common stock and restricted stock units (in shares)		273,461
Vesting of restricted common stock and restricted stock units	2		2
Repurchase of common stock for employee tax withholdings (in shares)		(39,328)
Repurchase of common stock for employee tax withholdings	(59)		(59)
Unrealized gains on marketable securities	0
Net loss	$ (16,598)				(16,598)
Balance at the end of the period (in shares) at Mar. 31, 2020	28,963,858	28,963,858
Balance at the end of the period at Mar. 31, 2020	$ 14,431	$ 29	$ 284,538	$ 0	$ (270,136)