Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Private Placement	Common Stock	Common Stock Private Placement	Treasury Stock	Additional Paid-In Capital	Additional Paid-In Capital Private Placement	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2019	$ 87,153		$ 23			$ 237,931			$ (150,801)
Beginning balance, Shares at Dec. 31, 2019			22,654,444
Issuance of common stock under employee benefit plans	286					286
Issuance of common stock under employee benefit plans, Shares			36,472
Vesting of restricted stock awards	4					4
Vesting of restricted stock awards, Shares			102,221
Repurchase of unvested restricted stock awards					8,787
Retirement of treasury shares					(8,787)
Stock-based compensation expense	1,693					1,693
Unrealized loss on marketable securities	(53)							$ (53)
Net loss	(18,452)								(18,452)
Ending balance at Mar. 31, 2020	70,631		$ 23			239,914		(53)	(169,253)
Ending balance, Shares at Mar. 31, 2020			22,793,137
Beginning balance at Dec. 31, 2019	87,153		$ 23			237,931			(150,801)
Beginning balance, Shares at Dec. 31, 2019			22,654,444
Unrealized loss on marketable securities	81
Net loss	(34,137)
Ending balance at Jun. 30, 2020	122,131		$ 27			306,961		81	(184,938)
Ending balance, Shares at Jun. 30, 2020			27,223,796
Beginning balance at Mar. 31, 2020	70,631		$ 23			239,914		(53)	(169,253)
Beginning balance, Shares at Mar. 31, 2020			22,793,137
Issuance of common stock		$ 64,317		$ 4			$ 64,313
Issuance of common stock, Shares				4,029,411
Issuance of common stock under employee benefit plans	525					525
Issuance of common stock under employee benefit plans, Shares			70,904
Vesting of restricted stock awards	5					5
Vesting of restricted stock awards, Shares			330,344
Repurchase of unvested restricted stock awards					10,642
Retirement of treasury shares					(10,642)
Stock-based compensation expense	2,204					2,204
Unrealized loss on marketable securities	134							134
Net loss	(15,685)								(15,685)
Ending balance at Jun. 30, 2020	122,131		$ 27			306,961		81	(184,938)
Ending balance, Shares at Jun. 30, 2020			27,223,796
Beginning balance at Dec. 31, 2020	95,181		$ 28			316,775		(2)	(221,620)
Beginning balance, Shares at Dec. 31, 2020			27,941,566
Issuance of common stock	47,407		$ 5			47,402
Issuance of common stock, Shares			4,600,000
Issuance of common stock under employee benefit plans	93					93
Issuance of common stock under employee benefit plans, Shares			11,888
Vesting of restricted stock awards	1					1
Vesting of restricted stock awards, Shares			40,982
Repurchase of unvested restricted stock awards					1,836
Retirement of treasury shares					(1,836)
Stock-based compensation expense	2,073					2,073
Unrealized loss on marketable securities	(2)							(2)
Net loss	(16,999)								(16,999)
Ending balance at Mar. 31, 2021	127,754		$ 33			366,344		(4)	(238,619)
Ending balance, Shares at Mar. 31, 2021			32,594,436
Beginning balance at Dec. 31, 2020	95,181		$ 28			316,775		(2)	(221,620)
Beginning balance, Shares at Dec. 31, 2020			27,941,566
Unrealized loss on marketable securities	(7)
Net loss	(36,647)
Ending balance at Jun. 30, 2021	110,890		$ 33			369,133		(9)	(258,267)
Ending balance, Shares at Jun. 30, 2021			32,659,740		21
Beginning balance at Mar. 31, 2021	127,754		$ 33			366,344		(4)	(238,619)
Beginning balance, Shares at Mar. 31, 2021			32,594,436
Issuance of common stock under employee benefit plans	242					242
Issuance of common stock under employee benefit plans, Shares			30,008
Vesting of restricted stock awards	1					1
Vesting of restricted stock awards, Shares			35,296
Repurchase of unvested restricted stock awards					2,435
Retirement of treasury shares					(2,414)
Stock-based compensation expense	2,546					2,546
Unrealized loss on marketable securities	(5)							(5)
Net loss	(19,648)								(19,648)
Ending balance at Jun. 30, 2021	$ 110,890		$ 33			$ 369,133		$ (9)	$ (258,267)
Ending balance, Shares at Jun. 30, 2021			32,659,740		21