Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Details)

v3.21.2
Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Accounting Policies [Abstract]        
Contract cost, amortization period 1 year   1 year  
Fuel revenue and fuel costs included fuel taxes $ 275.9 $ 131.6 $ 761.1 $ 348.7