Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Details)

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Fair Value Measurements - Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Details) - Fair Value Measurements Recurring - USD ($)
Jun. 30, 2022
Dec. 31, 2021
Assets:    
Total $ 216,686,000 $ 265,750,000
Level 1    
Assets:    
Total 132,092,000 114,052,000
Level 2    
Assets:    
Total 84,594,000 151,698,000
Level 3    
Assets:    
Total 0 0
Money Market Funds    
Assets:    
Total 61,187,000 29,451,000
Money Market Funds | Level 1    
Assets:    
Total 61,187,000 29,451,000
Commercial Paper    
Assets:    
Total 23,129,000 22,580,000
Commercial Paper | Level 2    
Assets:    
Total 23,129,000 22,580,000
Corporate Debt Securities    
Assets:    
Total 31,925,000 74,861,000
Corporate Debt Securities | Level 2    
Assets:    
Total 31,925,000 74,861,000
Equity Securities    
Assets:    
Total 34,008,000 37,181,000
Equity Securities | Level 1    
Assets:    
Total 34,008,000 37,181,000
Asset-backed Securities    
Assets:    
Total 8,583,000 32,957,000
Asset-backed Securities | Level 2    
Assets:    
Total 8,583,000 32,957,000
U.S. Government Securities    
Assets:    
Total 36,897,000 47,420,000
U.S. Government Securities | Level 1    
Assets:    
Total 36,897,000 47,420,000
U.S. Agency Securities    
Assets:    
Total 4,990,000  
U.S. Agency Securities | Level 2    
Assets:    
Total 4,990,000  
Supranational Debt Securities    
Assets:    
Total 15,967,000 21,300,000
Supranational Debt Securities | Level 2    
Assets:    
Total $ 15,967,000 $ 21,300,000