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Stock-Based Compensation, Equity Compensation Plans (Details)
3 Months Ended 12 Months Ended
Mar. 31, 2022
Plan
shares
Dec. 31, 2014
shares
Jun. 17, 2021
shares
Dec. 09, 2020
shares
Dec. 08, 2020
shares
Mar. 31, 2019
shares
Dec. 31, 2018
shares
Stock Options [Abstract]              
Number of equity compensation plans | Plan 3            
The Plans [Member]              
Stock Options [Abstract]              
Term of plan 10 years            
The Plans [Member] | Incentive Stock Options [Member]              
Stock Options [Abstract]              
Vesting period 4 years            
The Plans [Member] | Incentive Stock Options [Member] | Maximum [Member]              
Stock Options [Abstract]              
Term of option 10 years            
2014 Equity Incentive Plan [Member]              
Stock Options [Abstract]              
Number of shares authorized for issuance (in shares)   91,367 3,339,243     826,292  
Percentage of Common Stock outstanding used to determine annual increase in the plan limit   4.00%          
Shares available for grant (in shares) 1,325,499            
2018 Equity Incentive Plan [Member]              
Stock Options [Abstract]              
Number of shares authorized for issuance (in shares)             558,071
2019 Inducement Plan [Member]              
Stock Options [Abstract]              
Shares available for grant (in shares) 114,715            
Common stock reserved for issuance (in shares)       500,000 200,000