Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Capital Raises) (Narrative) (Details)

v3.22.1
Stockholders' Equity (Capital Raises) (Narrative) (Details) - USD ($)
 1 Months Ended 3 Months Ended
Mar. 04, 2022
Apr. 23, 2021
Oct. 23, 2020
Nov. 30, 2020
Mar. 31, 2022
Mar. 31, 2021
Runway Note [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Proceeds from issuance of notes $ 30,000,000.0       $ 30,000,000  
At the Market Offering [Member] | MLV & Co. and FBR Capital Markets & Co [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock offering, number of shares issued         2,400,000  
Stock offering, price per share         $ 1.80  
Stock offering, gross proceeds         $ 4,400,000  
Stock offering, aggregate fees paid         100,000  
Amount available for future stock offerings         $ 13,000,000.0  
At the Market Offering [Member] | Checkpoint [Member] | Common Stock [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock offering, number of shares issued         3,741,939 7,025,309
Stock offering, price per share         $ 2.19 $ 3.50
Stock offering, gross proceeds         $ 8,200,000 $ 24,600,000
Sale of stock, net proceeds         $ 8,000,000.0 $ 23,900,000
At the Market Offering [Member] | Checkpoint [Member] | Common Stock [Member] | Founders Agreement [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock offering, number of shares issued         93,542 175,625
Shares issued (in percent)         2.50%  
At the Market Offering [Member] | Mustang [Member] | Common Stock [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock offering, number of shares issued         2,800,000 11,600,000
Stock offering, price per share         $ 1.00 $ 4.17
Stock offering, gross proceeds         $ 2,800,000 $ 48,400,000
Stock offering, aggregate fees paid         $ 49,000 900,000
Sale of stock, net proceeds           $ 47,500,000
Shares issued (in percent)         2.50%  
At the Market Offering [Member] | Mustang [Member] | Common Stock [Member] | Founders Agreement [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock offering, number of shares issued         1,049,302 325,221
Number of Shares issuable for At-the-Market offering           63,688
Shares issued (in percent)         2.50%  
Shelf Registration Statement [Member] | Checkpoint [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Amount available for future stock offerings         $ 46,400,000  
Shelf Registration Statement [Member] | Mustang [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Amount available for future stock offerings         200,000,000  
Shelf Registration Statement [Member] | Maximum [Member] | Checkpoint [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock offering, aggregate offering permitted by the agreement       $ 100,000,000    
Shelf Registration Statement [Member] | Maximum [Member] | Mustang [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock offering, aggregate offering permitted by the agreement   $ 200,000,000        
Mustang 2020 S-3 [Member] | Mustang [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock offering, aggregate offering permitted by the agreement     $ 100,000,000.0      
Amount available for future stock offerings         $ 11,700,000