Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Unaudited) - USD ($) $ in Thousands	Total	Over-Allotment Option	Follow-On Public Offering	Voting Common Stock	Voting Common Stock Over-Allotment Option	Voting Common Stock Follow-On Public Offering	Additional Paid-in Capital	Additional Paid-in Capital Over-Allotment Option	Additional Paid-in Capital Follow-On Public Offering	Series A, A-1, B, B-1, C and D Convertible Preferred Stock (in equity)	Treasury Stock	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018				16,679,109						22,014,263	1,973,851
Beginning balance at Dec. 31, 2018	$ 25,733			$ 1			$ 1,844			$ 102,976	$ (10,507)	$ (68,581)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)				125,342
Exercise of stock options	62						62
Stock-based compensation expense	5,363						5,363
Net issuance of RSA grant (in shares)				242,155							192,281
Net issuance of RSA grant	(2,345)										$ (2,345)
Net loss	(20,957)											(20,957)
Ending balance (in shares) at Sep. 30, 2019				17,046,606						22,014,263	2,166,132
Ending balance at Sep. 30, 2019	7,856			$ 1			7,269			$ 102,976	$ (12,852)	(89,538)
Beginning balance (in shares) at Jun. 30, 2019				17,016,607						22,014,263	2,166,132
Beginning balance at Jun. 30, 2019	12,813			$ 1			7,187			$ 102,976	$ (12,852)	(84,499)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)				29,999
Exercise of stock options	17						17
Stock-based compensation expense	65						65
Net loss	(5,039)											(5,039)
Ending balance (in shares) at Sep. 30, 2019				17,046,606						22,014,263	2,166,132
Ending balance at Sep. 30, 2019	7,856			$ 1			7,269			$ 102,976	$ (12,852)	(89,538)
Beginning balance (in shares) at Dec. 31, 2019				48,844,998							2,673,805
Beginning balance at Dec. 31, 2019	128,130			$ 5			263,943				$ (20,430)	(115,388)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)				950,167
Exercise of stock options	362						362
Stock-based compensation expense	8,563						8,563
Issuance of common stock from equity award settlement (in shares)				826,611
Issuance of common stock from equity award settlement	0
Taxes paid related to net share settlement of equity awards (in shares)											270,732
Taxes paid related to net share settlement of equity awards	(6,335)										$ (6,335)
Issuance of common stock, net of underwriters' discounts, commissions and offering costs (in shares)					629,603	1,612,500
Issuance of common stock, net of underwriters' discounts, commissions and offering costs		$ 9,738	$ 41,936					$ 9,738	$ 41,936
Exercise of warrants (in shares)				26,960							8,345
Exercise of warrants	0						140				$ (140)
Net loss	(25,779)											(25,779)
Ending balance (in shares) at Sep. 30, 2020				52,890,839							2,952,882
Ending balance at Sep. 30, 2020	156,615			$ 5			324,682				$ (26,905)	(141,167)
Beginning balance (in shares) at Jun. 30, 2020				50,889,557							2,952,882
Beginning balance at Jun. 30, 2020	119,034			$ 5			280,104				$ (26,905)	(134,170)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)				242,081
Exercise of stock options	82						82
Stock-based compensation expense	2,560						2,560
Issuance of common stock from equity award settlement (in shares)				146,701
Issuance of common stock from equity award settlement	0
Issuance of common stock, net of underwriters' discounts, commissions and offering costs (in shares)						1,612,500
Issuance of common stock, net of underwriters' discounts, commissions and offering costs			$ 41,936						$ 41,936
Net loss	(6,997)											(6,997)
Ending balance (in shares) at Sep. 30, 2020				52,890,839							2,952,882
Ending balance at Sep. 30, 2020	$ 156,615			$ 5			$ 324,682				$ (26,905)	$ (141,167)