Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income [Member]
Beginning balances at Dec. 31, 2019	$ 153,536	$ 60	$ 512,231	$ (359,496)	$ 741
Beginning balance, Shares at Dec. 31, 2019		60,022,067
Exercise of stock options	132		132
Exercise of stock options, Shares		15,596
Stock-based compensation expense	3,172		3,172
Unrealized gains (losses) on available-for-sale securities	114				114
Net income (loss)	(14,282)			(14,282)
Ending balances at Mar. 31, 2020	142,672	$ 60	515,535	(373,778)	855
Ending balance, shares at Mar. 31, 2020		60,037,663
Beginning balances at Dec. 31, 2019	153,536	$ 60	512,231	(359,496)	741
Beginning balance, Shares at Dec. 31, 2019		60,022,067
Unrealized gains (losses) on available-for-sale securities	(201)
Net income (loss)	(50,570)
Ending balances at Jun. 30, 2020	271,393	$ 69	680,850	(410,066)	540
Ending balance, shares at Jun. 30, 2020		69,359,509
Beginning balances at Mar. 31, 2020	142,672	$ 60	515,535	(373,778)	855
Beginning balance, Shares at Mar. 31, 2020		60,037,663
Issuance of common stock in connection with public offerings, net of underwriting discounts and commissions and offering costs	153,611	$ 9	153,602
Issuance of common stock in connection with public offerings, net of underwriting discounts and commissions and offering costs, Shares		8,544,982
Exercise of stock options	5,699		5,699
Exercise of stock options, Shares		776,864
Stock-based compensation expense	6,014		6,014
Unrealized gains (losses) on available-for-sale securities	(315)				(315)
Net income (loss)	(36,288)			(36,288)
Ending balances at Jun. 30, 2020	271,393	$ 69	680,850	(410,066)	540
Ending balance, shares at Jun. 30, 2020		69,359,509
Beginning balances at Dec. 31, 2020	356,757	$ 75	769,965	(413,283)	0
Beginning balance, Shares at Dec. 31, 2020		75,029,625
Exercise of stock options	1,550		1,550
Exercise of stock options, Shares		188,047
Stock-based compensation expense	3,984		3,984
Unrealized gains (losses) on available-for-sale securities	77				77
Net income (loss)	26,522			26,522
Ending balances at Mar. 31, 2021	388,890	$ 75	775,499	(386,761)	77
Ending balance, shares at Mar. 31, 2021		75,217,672
Beginning balances at Dec. 31, 2020	356,757	$ 75	769,965	(413,283)	0
Beginning balance, Shares at Dec. 31, 2020		75,029,625
Unrealized gains (losses) on available-for-sale securities	35
Net income (loss)	43,666
Ending balances at Jun. 30, 2021	412,637	$ 75	782,144	(369,617)	35
Ending balance, shares at Jun. 30, 2021		75,343,712
Beginning balances at Mar. 31, 2021	388,890	$ 75	775,499	(386,761)	77
Beginning balance, Shares at Mar. 31, 2021		75,217,672
Exercise of stock options	819		819
Exercise of stock options, Shares		98,852
Issuance of common stock under employee stock purchase plan	490		490
Issuance of common stock under employee stock purchase plan, Shares		27,188
Stock-based compensation expense	5,336		5,336
Unrealized gains (losses) on available-for-sale securities	(42)				(42)
Net income (loss)	17,144			17,144
Ending balances at Jun. 30, 2021	$ 412,637	$ 75	$ 782,144	$ (369,617)	$ 35
Ending balance, shares at Jun. 30, 2021		75,343,712