Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurement (Details)

v3.21.2
Fair Value Measurement (Details) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value $ 454,933 $ 260,837
Level 1    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value (258) 41,923
Level 2    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 455,191 218,914
Level 3    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 0 0
Commercial paper    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 141,157 48,714
Commercial paper | Level 1    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 0 0
Commercial paper | Level 2    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 141,157 48,714
Commercial paper | Level 3    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 0 0
Corporate bonds    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 303,262 169,998
Corporate bonds | Level 1    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 0 0
Corporate bonds | Level 2    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 303,262 169,998
Corporate bonds | Level 3    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 0 0
U.S. Treasury bills    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value   44,992
U.S. Treasury bills | Level 1    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value   44,992
U.S. Treasury bills | Level 2    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value   0
U.S. Treasury bills | Level 3    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value   0
Municipal bonds    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 14,490 5,839
Municipal bonds | Level 1    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 0 0
Municipal bonds | Level 2    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 14,490 5,839
Municipal bonds | Level 3    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value 0 0
Commodity contract derivatives    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value (3,976) (8,706)
Commodity contract derivatives | Level 1    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value (258) (3,069)
Commodity contract derivatives | Level 2    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value (3,718) (5,637)
Commodity contract derivatives | Level 3    
Assets (liabilities) measured at fair value    
Assets (liabilities), fair value $ 0 $ 0