Stockholders' Equity - Narrative (Details)			1 Months Ended	12 Months Ended				20 Months Ended
	Mar. 02, 2020 shares	Nov. 26, 2019 $ / shares shares	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) vote shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2013 $ / shares shares	Dec. 31, 2021 USD ($) shares	May 31, 2020 USD ($)	Jul. 31, 2018 USD ($)
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)				25,000,000	25,000,000			25,000,000
Preferred stock, shares issued (in shares)				0	0			0
Number of shares into which warrant issued during period may be converted							129,491
Warrant exercise price per share (in dollars per share) | $ / shares							$ 0.05
Contractual life of warrants							10 years
Warrants outstanding (in shares)				39,474	39,474			39,474
Common stock issued upon exercise of warrant (in shares)				0
Number of shares reserved for future issuance (in shares)				9,199,512	6,869,189			9,199,512
Common Stock
Class of Stock [Line Items]
Issuance of common upon exercise of warrant (in shares)	2,574,971
Number of votes per common share | vote				1
Exchange Warrants
Class of Stock [Line Items]
Warrant exercise price per share (in dollars per share) | $ / shares		$ 0.0001
Warrants outstanding (in shares)				2,575,000				2,575,000
Number of common shares exchanged for warrants (in shares)		2,575,000
Number of shares of common stock into which warrants may be converted (in shares)		2,575,000
Warrants and share-based payment awards
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)				9,199,512	6,869,189			9,199,512
At market equity offering program (2018 ATM)
Class of Stock [Line Items]
Amount of shares authorized to be offered and sold | $										$ 75,000,000
Proceeds from issuance of common stock | $					$ 62,976,000
At market equity offering program (2018 ATM) | Common Stock
Class of Stock [Line Items]
Number of shares sold (in shares)					10,900,599
At market equity offering program (2018 ATM) | Additional Paid-in Capital
Class of Stock [Line Items]
Proceeds from issuance of common stock | $					$ 62,976,000
At Market Equity Offering Program (2020 ATM)
Class of Stock [Line Items]
Amount of shares authorized to be offered and sold | $									$ 100,000,000
Proceeds from issuance of common stock | $								$ 43,087,000
At Market Equity Offering Program (2020 ATM) | Common Stock
Class of Stock [Line Items]
Number of shares sold (in shares)								3,961,074
Public Stock Offering
Class of Stock [Line Items]
Number of shares sold (in shares)			9,200,000
Proceeds from issuance of common stock | $				$ 0	$ 163,990,000	$ 92,162,000
Shares sold, price per share (in dollars per share) | $ / shares			$ 19.00
Proceeds from stock issuance, net of issuance costs | $			$ 163,990,000
Public Stock Offering | Common Stock
Class of Stock [Line Items]
Number of shares sold (in shares)					9,200,000	24,437,500