Stockholders' Equity - Issuance of Common Stock and Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Nov. 25, 2019	Jun. 30, 2021	Jan. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued (in shares)						310,860	539,152
Exercise price of common stock (USD per share)				$ 3.59		$ 3.59
Amount paid for clearing fees		$ 19	$ 231
Offering costs paid on the issuance of common stock and warrants				$ 1	$ 0	$ 470	$ 474	$ 510
Proceeds from sale of common stock and warrants		$ 4,500	$ 2,300
Percentage of gross proceeds used to make payments on note			10.00%
Gross proceeds			$ 275
Payments on the Iliad Note				0	450	0	976
Proceeds from issuance of warrants						$ 1,100
Warrants exercised (in shares)						156,446
Proceeds from the exercise of warrants				$ 0	$ 625	$ 527	$ 676
Iliad Note
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of gross proceeds used to make payments on note	10.00%
Payments on the Iliad Note			$ 226
Institutional investors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of common stock (in shares)		990,100	688,360
Sale of common stock (USD per share)		$ 5.05	$ 3.37
Warrants issued (in shares)			688,360			269,180	497,472
Exercise price of common stock (USD per share)			$ 3.37	$ 3.3700	$ 3.3700	$ 3.3700	$ 3.3700
Purchase price (USD per share)			$ 0.625
Placement agent
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants issued (in shares)			48,185			41,680	41,680
Exercise price of common stock (USD per share)			$ 4.99	$ 4.9940	$ 4.9940	$ 4.9940	$ 4.9940
Amount paid for placement agent commissions		$ 400	$ 193
Amount paid related to expenses for registered direct offering and concurrent private placement		$ 51	$ 50