Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Beginning balance, common stock (in shares) at Dec. 31, 2018		32,941
Beginning balance at Dec. 31, 2018	$ 104,129	$ 33	$ 268,081	$ (78)	$ (163,907)
Exercises of common stock options (in shares)	24
Exercises of common stock options	$ 69		69
Vesting of restricted stock awards and restricted stock units (in shares)		2
Vesting of restricted stock units	7		7
Stock-based compensation expense	2,542		2,542
Other comprehensive income (loss)	129			129
Net loss	(12,377)				(12,377)
Ending balance (in shares) at Mar. 31, 2019		32,967
Ending balance at Mar. 31, 2019	$ 94,424	$ 33	270,699	51	(176,359)
Beginning balance, common stock (in shares) at Dec. 31, 2019	33,738	33,738
Beginning balance at Dec. 31, 2019	$ 174,593	$ 34	281,664	54	(107,159)
Issuance of common stock from at the market offering, net of issuance costs (in shares)		201
Issuance of common stock from at the market offering, net of issuance costs	$ 1,648		1,648
Exercises of common stock options (in shares)	9
Exercises of common stock options	$ 38		38
Vesting of restricted stock awards and restricted stock units (in shares)		101
Stock-based compensation expense	2,618		2,618
Other comprehensive income (loss)	90			90
Net loss	$ (26,443)				(26,443)
Ending balance (in shares) at Mar. 31, 2020	34,049	34,049
Ending balance at Mar. 31, 2020	$ 152,544	$ 34	$ 285,968	$ 144	$ (133,602)