Stockholders' Equity - Additional Information (Details) - USD ($)	1 Months Ended					3 Months Ended	12 Months Ended
	Aug. 31, 2020	Apr. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Aug. 31, 2017	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Net proceeds from sale of common stock							$ 10,664,000	$ 7,397,000	$ 43,926,000
Common Stock | 2019 Underwriters
Class Of Stock [Line Items]
Common stock price per share				$ 4.00
Common Stock | Citigroup Global Markets, Inc
Class Of Stock [Line Items]
Common stock price per share		$ 6.25
Underwriting Agreement | 2019 Underwriters
Class Of Stock [Line Items]
Net proceeds from sale of common stock				$ 53,800,000
Underwriting Agreement | Citigroup Global Markets, Inc
Class Of Stock [Line Items]
Net proceeds from sale of common stock		$ 33,500,000
Underwriting Agreement | Common Stock | 2019 Underwriters
Class Of Stock [Line Items]
Number of shares issued and sold				14,375,000
Number of shares sold pursuant to the Underwriters' option to purchase additional shares				1,875,000
Common stock price per share				$ 3.76
Underwriting Agreement | Common Stock | Citigroup Global Markets, Inc
Class Of Stock [Line Items]
Number of shares issued and sold		5,750,000
Number of shares sold pursuant to the Underwriters' option to purchase additional shares		750,000
Common stock price per share		$ 5.88
2017 ATM Program | Common Stock | Cowen and Company LLC
Class Of Stock [Line Items]
Aggregate maximum offering price					$ 50,000,000.0
2017 ATM Program | Common Stock | Cowen and Company LLC | Maximum
Class Of Stock [Line Items]
Percentage of sales commission on gross proceeds for common stock sold through sales agreement					3.00%
2019 ATM Program | Common Stock | Jefferies LLC
Class Of Stock [Line Items]
Number of shares issued and sold						1,160,425
Net proceeds from sale of common stock						$ 7,400,000
Aggregate maximum offering price									$ 50,000,000.0
Shares sold, average price per share			$ 6.51			$ 6.51
Gross proceeds from sale of common stock						$ 7,600,000
2019 ATM Program | Common Stock | Jefferies LLC | Maximum
Class Of Stock [Line Items]
Percentage of sales commission on gross proceeds for common stock sold through sales agreement									3.00%
2017 and 2019 ATM program | Common Stock | Jefferies LLC
Class Of Stock [Line Items]
Number of shares issued and sold									9,929,742
Net proceeds from sale of common stock									$ 44,000,000.0
Shares sold, average price per share									$ 4.54
Gross proceeds from sale of common stock									$ 45,100,000
March 2020 ATM Program | Common Stock | Jefferies LLC
Class Of Stock [Line Items]
Number of shares issued and sold							5,245,410
Net proceeds from sale of common stock							$ 10,700,000
Shares sold, average price per share							$ 2.18
Gross proceeds from sale of common stock							$ 11,400,000
Proceeds receivable from unsettled trades							$ 451,000
March 2020 ATM Program | Common Stock | Jefferies LLC | Maximum
Class Of Stock [Line Items]
Percentage of sales commission on gross proceeds for common stock sold through sales agreement			3.00%
August 2020 ATM Program | Common Stock | Jefferies LLC
Class Of Stock [Line Items]
Number of shares issued and sold							5,245,410
Aggregate maximum offering price	$ 75,000,000.0
Common stock remained available for sale							$ 63,600,000
August 2020 ATM Program | Common Stock | Jefferies LLC | Maximum
Class Of Stock [Line Items]
Percentage of sales commission on gross proceeds for common stock sold through sales agreement	3.00%