Quarterly report pursuant to Section 13 or 15(d)

Cash Equivalents and Marketable Securities - Schedule of Cash Equivalents and Marketable Securities (Details)

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Cash Equivalents and Marketable Securities - Schedule of Cash Equivalents and Marketable Securities (Details) - USD ($)
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Cash And Cash Equivalents [Line Items]      
Amortized Cost Basis $ 292,845,000 $ 324,845,000  
Unrealized Gains 65,000 131,000  
Unrealized (Losses) (64,000) (3,000)  
Fair Value 292,846,000 324,973,000  
Less amounts classified as cash equivalents, Amortized Cost Basis (55,818,000) (206,152,000) $ (43,565,000)
Marketable Securities      
Cash And Cash Equivalents [Line Items]      
Amortized Cost Basis 239,069,000 120,213,000  
Unrealized Gains 65,000 131,000  
Unrealized (Losses) (64,000) (3,000)  
Fair Value 239,070,000 120,341,000  
Cash Equivalents      
Cash And Cash Equivalents [Line Items]      
Less amounts classified as cash equivalents, Amortized Cost Basis (53,776,000) (204,632,000)  
Less amounts classified as cash equivalents, Fair Value (53,776,000) (204,632,000)  
Money Market Funds      
Cash And Cash Equivalents [Line Items]      
Amortized Cost Basis 53,776,000 204,632,000  
Unrealized Gains 0 0  
Unrealized (Losses) 0 0  
Fair Value 53,776,000 204,632,000  
Commercial Paper      
Cash And Cash Equivalents [Line Items]      
Amortized Cost Basis 64,344,000 42,208,000  
Unrealized Gains 0 0  
Unrealized (Losses) 0 0  
Fair Value 64,344,000 42,208,000  
Corporate Debt Securities      
Cash And Cash Equivalents [Line Items]      
Amortized Cost Basis 64,708,000 25,669,000  
Unrealized Gains 14,000 48,000  
Unrealized (Losses) (44,000) (1,000)  
Fair Value 64,678,000 25,716,000  
Asset-backed Securities      
Cash And Cash Equivalents [Line Items]      
Amortized Cost Basis 36,881,000 12,593,000  
Unrealized Gains 18,000 39,000  
Unrealized (Losses) (10,000) 0  
Fair Value 36,889,000 12,632,000  
U.S. Government Securities      
Cash And Cash Equivalents [Line Items]      
Amortized Cost Basis 59,832,000 39,743,000  
Unrealized Gains 33,000 44,000  
Unrealized (Losses) 0 (2,000.00)  
Fair Value 59,865,000 $ 39,785,000  
Supranational Debt Securities      
Cash And Cash Equivalents [Line Items]      
Amortized Cost Basis 13,304,000    
Unrealized Gains 0    
Unrealized (Losses) (10,000)    
Fair Value $ 13,294,000