Stockholders' Equity - Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended		12 Months Ended
	Mar. 14, 2022	Oct. 08, 2021	Feb. 21, 2020	Aug. 31, 2019	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 10, 2022	Oct. 31, 2021	Sep. 30, 2021	Mar. 18, 2021	Feb. 28, 2021	Feb. 10, 2021	Oct. 02, 2020	Feb. 10, 2020	Nov. 08, 2019	Jan. 23, 2019
Sale of stock
Common stock that can be purchased with warrants (in shares)										13,333,324			450,000
Proceeds from issuance of common stock in private placement, net of offering costs								$ 7,810
Number of warrants outstanding (in shares)										13,333,324			450,000
Perceptive Warrants | Perceptive Credit Agreement
Sale of stock
Common stock that can be purchased with warrants (in shares)										1,850,000						1,400,000
Exercise price of warrants (in dollars per share)														$ 2.87
Number of warrants outstanding (in shares)										1,850,000						1,400,000
First Seven Lakhs Shares | Perceptive Credit Agreement
Sale of stock
Common stock that can be purchased with warrants (in shares)										700,000						700,000
Exercise price of warrants (in dollars per share)										$ 3.83	$ 4.67					$ 3.74
Number of warrants outstanding (in shares)										700,000						700,000
Remaining Seven Lakhs Shares | Perceptive Credit Agreement
Sale of stock
Common stock that can be purchased with warrants (in shares)										700,000						700,000
Exercise price of warrants (in dollars per share)										$ 3.11	3.74					$ 4.67
Number of warrants outstanding (in shares)										700,000						700,000
Warrants | Perceptive Credit Agreement
Sale of stock
Common stock that can be purchased with warrants (in shares)										450,000
Exercise price of warrants (in dollars per share)										$ 2.43	$ 2.87
Number of warrants outstanding (in shares)										450,000
2020 Shelf Registration Statement
Sale of stock
Aggregate amount of securities issuable															$ 200,000
Proceeds from issuance of common stock in public offering, net of offering costs	$ 4,300
Conversion price	$ 0.20
Preferred Stock, convertible, shares issuable	24,250,000
Stock stated value	$ 1,000
2020 Shelf Registration Statement | Series A Warrants
Sale of stock
Common stock that can be purchased with warrants (in shares)	24,250,000
Number of warrants outstanding (in shares)	24,250,000
2020 Shelf Registration Statement | Series B Warrants
Sale of stock
Common stock that can be purchased with warrants (in shares)	24,250,000
Number of warrants outstanding (in shares)	24,250,000
2018 Shelf Registration Statement
Sale of stock
Aggregate amount of securities issuable															$ 100,000
Private Placement | Common stock
Sale of stock
Issuance of common stock (in shares)					8,426,750			8,426,750
Share price (in dollars per share)					$ 0.93
Proceeds from issuance of common stock in public offering, net of offering costs					$ 7,800
At-the-market sales | Maximum
Sale of stock
Authorized value for shares issuance																	$ 20,000	$ 10,000
At-the-market sales | Common stock
Sale of stock
Issuance of common stock (in shares)						6,915,151		12,242,436
At-the-market sales | Common stock | Maximum
Sale of stock
Authorized value for shares issuance												$ 50,000
At-the-market sales | Common stock | Maximum | Subsequent event
Sale of stock
Authorized value for shares issuance									$ 50,000
At Market Sales on January 23
Sale of stock
Proceeds from issuance of common stock in public offering, net of offering costs							$ 2,500
At Market Sales on January 23 | Common stock
Sale of stock
Issuance of common stock (in shares)							1,801,528
At Market Sales on November 8
Sale of stock
Proceeds from issuance of common stock in public offering, net of offering costs							$ 19,300
At Market Sales on November 8 | Common stock
Sale of stock
Issuance of common stock (in shares)							10,440,908
At Market Sales on March 18 | Common stock
Sale of stock
Issuance of common stock (in shares)						6,915,151
Proceeds from issuance of common stock in public offering, net of offering costs						$ 9,300
Public offering
Sale of stock
Proceeds from issuance of common stock in public offering, net of offering costs						$ 21,081	$ 48,434	$ 12,687
Public offering | Common stock
Sale of stock
Issuance of common stock (in shares)		26,666,648	17,250,000	14,526,315		26,666,648	17,250,000	14,526,315
Common stock that can be purchased with warrants (in shares)		13,333,324
Common stock that can be purchased with one-half of warrant (in shares)		1
Share price (in dollars per share)		$ 0.85	$ 3.00	$ 0.95
Proceeds from issuance of common stock in public offering, net of offering costs		$ 21,100	$ 48,400	$ 12,700
Number of warrants outstanding (in shares)		13,333,324
Series A Preferred Stock | 2020 Shelf Registration Statement
Sale of stock
Issuance of common stock (in shares)	2,425
Series B Preferred Stock | 2020 Shelf Registration Statement
Sale of stock
Issuance of common stock (in shares)	2,425