Quarterly report pursuant to Section 13 or 15(d)

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

v3.21.2
Fair Value Measurements - Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Details) - Fair Value Measurements Recurring - USD ($)
Jun. 30, 2021
Dec. 31, 2020
Assets:    
Total $ 320,282,000 $ 366,617,000
Level 1    
Assets:    
Total 138,458,000 286,061,000
Level 2    
Assets:    
Total 181,824,000 80,556,000
Level 3    
Assets:    
Total 0 0
Money Market Funds    
Assets:    
Total 57,964,000 204,632,000
Money Market Funds | Level 1    
Assets:    
Total 57,964,000 204,632,000
Commercial Paper    
Assets:    
Total 59,361,000 42,208,000
Commercial Paper | Level 2    
Assets:    
Total 59,361,000 42,208,000
Corporate Debt Securities    
Assets:    
Total 71,419,000 25,716,000
Corporate Debt Securities | Level 2    
Assets:    
Total 71,419,000 25,716,000
Equity Securities    
Assets:    
Total 35,280,000 41,644,000
Equity Securities | Level 1    
Assets:    
Total 35,280,000 41,644,000
Asset-backed Securities    
Assets:    
Total 37,792,000 12,632,000
Asset-backed Securities | Level 2    
Assets:    
Total 37,792,000 12,632,000
U.S. Government Securities    
Assets:    
Total 45,214,000 39,785,000
U.S. Government Securities | Level 1    
Assets:    
Total 45,214,000 $ 39,785,000
Supranational Debt Securities    
Assets:    
Total 13,252,000  
Supranational Debt Securities | Level 2    
Assets:    
Total $ 13,252,000