Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Narrative (Details)

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Summary of Significant Accounting Policies - Narrative (Details) - USD ($)
3 Months Ended
Sep. 13, 2021
Feb. 11, 2021
Mar. 31, 2022
Mar. 31, 2021
Dec. 31, 2021
Class of Stock [Line Items]          
Working capital surplus     $ 74,300,000    
Cash and cash equivalents     60,852,000   $ 52,480,000
Short-term investments     15,035,000   $ 43,125,000
Net income (loss)     $ (11,557,000) $ (12,539,000)  
Preferred stock, shares authorized (in shares)     5,000,000   5,000,000
Number of shares sold under offering (in shares)   3,000,000      
Net proceeds from issuance of preferred stock and warrants $ 50,600,000   $ 46,906,000 0  
Unrealized loss on available for sale securities     89,000 2,000  
Unrealized loss on equity securities     $ 1,503,000 0  
Stated term     1 year    
Renewal option term     1 year    
Term for students     2 years    
Deferred revenue     $ 4,100,000   $ 4,800,000
Stock based compensation     $ 1,533,000 $ 5,096,000  
Series 8 Convertible Preferred Stock          
Class of Stock [Line Items]          
Preferred stock, shares authorized (in shares)     53,197.7234    
Number of shares sold under offering (in shares)     112,778,720    
Subscription price (in usd per share)     $ 940    
Original issuance discount percentage     6.00%    
Aggregate subscription value     $ 50,000,000.0    
Net proceeds from issuance of preferred stock and warrants     $ 46,900,000