STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Common stock, outstanding (in shares) at Dec. 31, 2018		23,401,675
Balance at Dec. 31, 2018	$ 163,999	$ 23	$ 310,941	$ (52)	$ (146,913)
Stockholders' Equity [Roll Forward]
Stock options exercised (in shares)		100,089
Stock options exercised	166	$ 1	165
Issuance of common stock (in shares)		1,246
Issuance of common stock	58		58
Stock-based compensation expense	1,391		1,391
Other comprehensive income (loss)	68			68
Net loss	(8,266)				(8,266)
Common stock, outstanding (in shares) at Mar. 31, 2019		23,503,010
Balance at Mar. 31, 2019	$ 157,416	$ 24	312,555	16	(155,179)
Common stock, outstanding (in shares) at Dec. 31, 2019	24,107,350	24,107,350
Balance at Dec. 31, 2019	$ 139,835	$ 24	319,865	102	(180,156)
Stockholders' Equity [Roll Forward]
Stock options exercised (in shares)	254,142	254,142
Stock options exercised	$ 787		787
Issuance of common stock (in shares)		897
Issuance of common stock	72		72
Stock-based compensation expense	2,749		2,749
Other comprehensive income (loss)	193			193
Net loss	$ (16,245)				(16,245)
Common stock, outstanding (in shares) at Mar. 31, 2020	24,362,389	24,362,389
Balance at Mar. 31, 2020	$ 127,403	$ 24	$ 323,473	$ 295	$ (196,389)