Warrants - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended				3 Months Ended	12 Months Ended
	Jan. 31, 2017	Sep. 30, 2016	Aug. 31, 2015	Jul. 31, 2015	Mar. 31, 2018	Dec. 31, 2021	Dec. 31, 2018	Dec. 31, 2020
Common Stock Warrants [Line Items]
Placement warrants not exercised and remained outstanding (in shares)						2,036,733		2,156,153
Proceed from private placement and equity issuances, gross	$ 26.1	$ 13.8
Fair value of warrants upon issuance	$ 3.4	$ 2.7
2018 Direct Registered Offering | Common Stock
Common Stock Warrants [Line Items]
Warrants issued (in shares)					1,418,116
Warrant exercise price (in dollars per share)					$ 8.31
Number of warrant exercised (in shares)						0
Proceed from private placement and equity issuances, gross					$ 59.1
Fair value of warrants upon issuance					7.4
Allocated portion of proceeds from issuance of stock and warrants recorded in additional paid-in-capital					$ 6.6
2015 Placement Warrants
Common Stock Warrants [Line Items]
Warrants issued (in shares)			198,760	198,760
Warrant exercise price (in dollars per share)			$ 5.00	$ 5.00
Common stock warrants, expiry term (in years)			5 years	5 years
Shares issued from stock warrant exercises (in shares)							92,487
Number of warrant exercised (in shares)							159,010
Number of warrant expired (in shares)			39,750	39,750
Placement warrants not exercised and remained outstanding (in shares)						0
2016 Placement Warrants Liability
Common Stock Warrants [Line Items]
Warrants issued (in shares)		1,380,745
Warrant exercise price (in dollars per share)						$ 2.95
Placement warrants not exercised and remained outstanding (in shares)						536,711		537,263
2017 Placement Warrants Liability
Common Stock Warrants [Line Items]
Warrants issued (in shares)	1,720,512
Warrant exercise price (in dollars per share)						$ 3.17
Placement warrants not exercised and remained outstanding (in shares)						1,500,022		1,618,890