Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Adoption of new accounting pronouncement	Common Stock	Additional Paid-In Capital	Additional Paid-In Capital Adoption of new accounting pronouncement	Accumulated Deficit	Accumulated Deficit Adoption of new accounting pronouncement	Treasury Stock	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2018			26,824,859
Beginning balance at Dec. 31, 2018	$ 79,118		$ 27	$ 677,511		$ (598,101)		$ 0	$ (319)
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)			649,529
Exercise of stock options	11,771			11,771
Exercise of warrants (in shares)			5,813
Exercise of warrants	0
Vesting of restricted stock units (in shares)			17,710
Vesting of restricted stock units	0
Stock-based compensation	25,884			25,884
Other comprehensive gain (loss)	342								342
Net loss	(97,165)					(97,165)
Ending balance (in shares) at Dec. 31, 2019			27,497,911
Ending balance at Dec. 31, 2019	19,950		$ 27	715,166		(695,266)		0	23
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)			299,435
Exercise of stock options	6,634		$ 1	6,633
Vesting of restricted stock units (in shares)			113,020
Vesting of restricted stock units	0
Stock-based compensation	28,385			28,385
Other comprehensive gain (loss)	(23)								(23)
Equity component of convertible notes	93,475			93,475
Repurchase of common stock under prepaid forward contract (in shares)			(1,994,198)
Repurchase of common stock under prepaid forward contract	(55,000)		$ (2)					(54,998)
Capped call options associated with convertible notes	(46,004)			(46,004)
Net loss	(143,551)					(143,551)
Ending balance (in shares) at Dec. 31, 2020			25,916,168
Ending balance at Dec. 31, 2020	(96,134)	$ (91,927)	$ 26	797,655	$ (93,475)	(838,817)	$ 1,548	(54,998)	0
Increase (Decrease) in Stockholders' Equity
Issuance of common stock and warrants from offering, net of issuance costs (in shares)			32,142,858
Issuance of common stock and warrants from offering, net of issuance costs	208,730		$ 32	208,698
Issuance of common stock, net of issuance costs (in shares)			897,364
Issuance of common stock and warrants from offering, net of issuance costs	9,703		$ 1	9,702
Exchange of $15 million of convertible note to equity, net of issuance costs (in shares)			1,094,848
Exchange of convertible notes to equity, net of issuance costs	$ 11,660		$ 1	11,659
Exercise of stock options (in shares)	491,700		491,700
Exercise of stock options	$ 3,762		$ 1	3,761
Vesting of restricted stock units (in shares)			203,344
Vesting of restricted stock units	0
Vesting of ESPP Shares (in shares)			133,214
Vesting of ESPP Shares	2,095			2,095
Stock-based compensation	24,306			24,306
Other comprehensive gain (loss)	(31)								(31)
Net loss	(269,108)					(269,108)
Ending balance (in shares) at Dec. 31, 2021			60,879,496
Ending balance at Dec. 31, 2021	$ (196,944)		$ 61	$ 964,401		$ (1,106,377)		$ (31)	$ (54,998)