Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Fair Value Measured on a Recurring Basis (Details)

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Fair Value Measurements - Fair Value Measured on a Recurring Basis (Details) - USD ($)
$ in Thousands
Jun. 30, 2021
Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value $ 37,826 $ 37,813
Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 37,826 37,813
Warrant liabilities 0 (17,740)
Total warrant liabilities at fair value 0 (17,740)
Fair Value, Inputs, Level 1, 2 and 3 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 34,412 37,756
Level 1 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 15,969 5,380
Warrant liabilities 0 0
Total warrant liabilities at fair value 0 0
Level 2 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 18,443 32,376
Warrant liabilities 0 0
Total warrant liabilities at fair value 0 0
Level 3 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 0 0
Warrant liabilities 0 (17,740)
Total warrant liabilities at fair value 0 (17,740)
Commercial paper | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 16,691 11,932
Commercial paper | Level 1 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 0 0
Commercial paper | Level 2 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 16,691 11,932
Commercial paper | Level 3 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 0 0
U.S. Treasuries | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 15,969 5,380
U.S. Treasuries | Level 1 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 15,969 5,380
U.S. Treasuries | Level 2 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 0 0
U.S. Treasuries | Level 3 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 0 0
Corporate bonds | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 1,752 20,444
Corporate bonds | Level 1 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 0 0
Corporate bonds | Level 2 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 1,752 20,444
Corporate bonds | Level 3 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value 0 0
Money Market Funds | Fair Value Measured at Net Asset Value Per Share | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total investments at fair value $ 3,414 $ 57