CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Gain (Loss)
Balances at Dec. 31, 2020	$ 210,947	$ 310	$ 1,366,188	$ (1,155,629)	$ 78
Balances (in shares) at Dec. 31, 2020		310,566,853
Increase (Decrease) in Stockholders' Equity
Net loss	(27,824)			(27,824)
Other comprehensive loss	(43)				(43)
Issuance of common stock in connection with at market offering, net of issuance costs	16,234	$ 8	16,226
Issuance of common stock in connection with at market offering, net of issuance costs (in shares)		7,948,505
Stock-based compensation related to issuance of common stock and options in exchange for services	25		25
Stock-based compensation related to issuance of common stock and options in exchange for services (in shares)		4,549
Issuance of common stock in connection with exercise of warrants	12		12
Issuance of common stock in connection exercise of warrants (in shares)		8,869
Issuances of common stock under equity plans	17		17
Issuances of common stock under equity plans (in shares)		16,232
Stock-based compensation for equity-based awards to employees and directors	1,794		1,794
Balances at Mar. 31, 2021	201,162	$ 318	1,384,262	(1,183,453)	35
Balances (in shares) at Mar. 31, 2021		318,545,008
Balances at Dec. 31, 2020	210,947	$ 310	1,366,188	(1,155,629)	78
Balances (in shares) at Dec. 31, 2020		310,566,853
Increase (Decrease) in Stockholders' Equity
Net loss	(57,398)
Balances at Jun. 30, 2021	176,206	$ 321	1,388,909	(1,213,027)	3
Balances (in shares) at Jun. 30, 2021		320,599,195
Balances at Mar. 31, 2021	201,162	$ 318	1,384,262	(1,183,453)	35
Balances (in shares) at Mar. 31, 2021		318,545,008
Increase (Decrease) in Stockholders' Equity
Net loss	(29,574)			(29,574)
Other comprehensive loss	(32)				(32)
Stock-based compensation related to issuance of common stock and options in exchange for services	23		23
Stock-based compensation related to issuance of common stock and options in exchange for services (in shares)		5,097
Issuance of common stock in connection with exercise of warrants	2,467	$ 2	2,465
Issuance of common stock in connection exercise of warrants (in shares)		1,897,472
Issuances of common stock under equity plans	187	$ 1	186
Issuances of common stock under equity plans (in shares)		151,618
Stock-based compensation for equity-based awards to employees and directors	1,973		1,973
Balances at Jun. 30, 2021	176,206	$ 321	1,388,909	(1,213,027)	3
Balances (in shares) at Jun. 30, 2021		320,599,195
Balances at Dec. 31, 2021	126,416	$ 324	1,398,006	(1,271,741)	(173)
Balances (in shares) at Dec. 31, 2021		323,731,591
Increase (Decrease) in Stockholders' Equity
Net loss	(30,098)			(30,098)
Other comprehensive loss	(538)				(538)
Stock-based compensation related to issuance of common stock and options in exchange for services	15		15
Stock-based compensation related to issuance of common stock and options in exchange for services (in shares)		5,284
Stock-based compensation for equity-based awards to employees and directors	1,692		1,692
Balances at Mar. 31, 2022	97,487	$ 324	1,399,713	(1,301,839)	(711)
Balances (in shares) at Mar. 31, 2022		323,736,875
Balances at Dec. 31, 2021	126,416	$ 324	1,398,006	(1,271,741)	(173)
Balances (in shares) at Dec. 31, 2021		323,731,591
Increase (Decrease) in Stockholders' Equity
Net loss	(58,215)
Balances at Jun. 30, 2022	142,047	$ 378	1,472,407	(1,329,956)	(782)
Balances (in shares) at Jun. 30, 2022		377,664,759
Balances at Mar. 31, 2022	97,487	$ 324	1,399,713	(1,301,839)	(711)
Balances (in shares) at Mar. 31, 2022		323,736,875
Increase (Decrease) in Stockholders' Equity
Net loss	(28,117)			(28,117)
Other comprehensive loss	(71)				(71)
Issuance of common stock, pre-funded warrant and warrants to purchase common stock in public offering, net of issuance costs	69,916	$ 53	69,863
Issuance of common stock, pre-funded warrant and warrants to purchase common stock in public offering, net of issuance costs, (in shares)		53,333,334
Stock-based compensation related to issuance of common stock and options in exchange for services	13		13
Stock-based compensation related to issuance of common stock and options in exchange for services (in shares)		4,637
Issuances of common stock under equity plans	761	$ 1	760
Issuances of common stock under equity plans (in shares)		589,913
Stock-based compensation for equity-based awards to employees and directors	2,058		2,058
Balances at Jun. 30, 2022	$ 142,047	$ 378	$ 1,472,407	$ (1,329,956)	$ (782)
Balances (in shares) at Jun. 30, 2022		377,664,759