Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Public Offering	At-the-Market Offering	Common Stock	Common Stock Public Offering	Common Stock At-the-Market Offering	Additional Paid-In Capital	Additional Paid-In Capital Cumulative Effect, Period of Adoption, Adjustment	Additional Paid-In Capital Public Offering	Additional Paid-In Capital At-the-Market Offering	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2018	$ 126,714				$ 4			$ 322,993				$ (196,170)		$ (113)
Balance, shares at Dec. 31, 2018					38,834,000
Issuance of common stock			$ 53,761	$ 43,968		$ 1	$ 1			$ 53,760	$ 43,967
Issuance of common stock, shares						14,375,000	9,929,000
Issuance of common stock pursuant to equity incentive plans	1,222							1,222
Issuance of common stock pursuant to equity incentive plans, shares					376,000
Stock-based compensation expense	6,466							6,466
Cumulative-effect adjustment from adoption of accounting standard | ASC 2018-07									$ 71				$ (71)
Net loss	(89,860)											(89,860)
Unrealized gain (loss) on available-for-sale securities	155													155
Balance at Dec. 31, 2019	142,426				$ 6			428,479				(286,101)		42
Balance, shares at Dec. 31, 2019					63,514,000
Issuance of common stock			$ 33,464	7,397		$ 1				$ 33,463	7,397
Issuance of common stock, shares						5,750,000	1,160,000
Issuance of common stock pursuant to equity incentive plans	1,200							1,200
Issuance of common stock pursuant to equity incentive plans, shares					262,000
Stock-based compensation expense	8,060							8,060
Net loss	(90,137)											(90,137)
Unrealized gain (loss) on available-for-sale securities	(39)													(39)
Balance at Dec. 31, 2020	$ 102,371				$ 7			478,599				(376,238)		3
Balance, shares at Dec. 31, 2020					70,686,000
Temporary equity, Balance, shares at Dec. 31, 2020	0
Issuance of series A convertible preferred stock, net of issuance costs of $173		$ 40,702
Issuance of series A convertible preferred stock, net of issuance costs of $173, shares		1,000,000
Issuance of common stock				$ 10,661			$ 1				$ 10,660
Issuance of common stock, shares							5,245,000
Issuance of common stock pursuant to equity incentive plans	$ 177							177
Issuance of common stock pursuant to equity incentive plans, shares					1,213,000
Stock-based compensation expense	10,264							10,264
Net loss	(115,088)											(115,088)
Unrealized gain (loss) on available-for-sale securities	(3)													$ (3)
Balance at Dec. 31, 2021	8,382				$ 8			$ 499,700				$ (491,326)
Balance, shares at Dec. 31, 2021					77,144,000
Temporary equity, Balance at Dec. 31, 2021	$ 40,702	$ 40,702
Temporary equity, Balance, shares at Dec. 31, 2021	1,000,000	1,000,000