Stock Based Compensation - Stock Compensation Expense, Restricted Stock (Details) - Restricted Stock - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock compensation expense	$ 0	$ 0
Shares of common stock issuable upon conversion of Series D preferred stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock compensation expense	33,000	158,000
Research and Development Expense | Shares of common stock issuable upon conversion of Series D preferred stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock compensation expense	17,000	47,000
Sales, general and administrative | Shares of common stock issuable upon conversion of Series D preferred stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock compensation expense	$ 16,000	$ 111,000