Stockholders' Equity - Stock Options and Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Stock Options, Shares
Options, Outstanding, Beginning of Period (in shares)	2,131,849
Options, Granted (in shares)	540,600
Options, Exercised (in shares)	0
Options, Forfeited (in shares)	(9,565)
Options, Expired (in shares)	(23,275)
Options, Outstanding, End of Period (in shares)	2,639,609	2,131,849
Options, Vested and expected to vest (in shares)	2,594,630
Options, Vested (in shares)	1,408,083
Stock Options, Weighted Average Exercise Price
Options, Outstanding. Beginning of Period (in dollars per share)	$ 5.64
Options, Granted (in dollars per share)	0.91
Options, Exercised (in dollars per share)	0
Options, Forfeited (in dollars per share)	1.90
Options, Expired (in dollars per share)	26.00
Options, Outstanding, End of Period (in dollars per share)	4.51	$ 5.64
Options, Vested and expected to vest (in dollars per share)	4.57
Options, Vested (in dollars per share)	$ 7.36
Stock Options, Weighted Average Contractual Term and Intrinsic Value
Options, Outstanding, Weighted Average Remaining Contractual Term	7 years 9 months 29 days	7 years 11 months 19 days
Options, Vested and expected to vest, Weighted Average Remaining Contractual Term	7 years 9 months 18 days
Options, Vested, Weighted Average Remaining Contractual Term	6 years 4 months 28 days
Options, Outstanding, Aggregate Intrinsic Value	$ 0	$ 0
Options, Vested and expected to vest, Aggregate Intrinsic Value	0
Options, Vested, Aggregate Intrinsic Value	$ 0
Warrants, Shares
Warrants, Outstanding, Beginning of Period (in shares)	21,356,600
Warrants, Granted (in shares)	0
Warrants, Exercised (in shares)	0
Warrants, Forfeited (in shares)	0
Warrants, Expired (in shares)	0
Warrants, Outstanding, End of Period (in shares)	21,356,600	21,356,600
Warrants, Vested and expected to vest (in shares)	21,356,600
Warrants, Vested (in shares)	21,356,600
Warrants, Weighted Average Exercise Price
Warrants Outstanding, Beginning of Period (in dollars per share)	$ 2.84
Warrants, Granted (in dollars per share)	0
Warrants, Exercised (in dollars per share)	0
Warrants, Forfeited (in dollars per share)	0
Warrants, Expired (in dollars per share)	0
Warrants Outstanding, End of Period (in dollars per share)	2.84	$ 2.84
Weighted Average Exercise Price, Warrants Vested And Expected To Vest	2.84
Warrants, Vested, Weighted Average Exercise Price (in dollars per share)	$ 2.84
Warrants, Weighted Average Contractual Term and Intrinsic Value
Warrants, Outstanding, Weighted Average Remaining Contractual Term	4 years 1 month 17 days	4 years 4 months 13 days
Warrants, Vested and expected to vest, Weighted Average Remaining Contractual Term	4 years 1 month 17 days
Warrants, Vested, Weighted Average Remaining Contractual Term	4 years 1 month 17 days
Warrants Outstanding, Aggregate Intrinsic Value	$ 0	$ 0
Warrants, Vested and expected to vest, Aggregate Intrinsic Value	0
Warrants, Vested, Aggregate Intrinsic Value	$ 0