Fair Value Measurements and Derivative Instruments - Fuel Price Risk (Details) - Fuel Swap Agreements $ in Millions		3 Months Ended	9 Months Ended
		Sep. 30, 2021 USD ($) T	Sep. 30, 2022 USD ($) T t	Sep. 30, 2021 USD ($) T	Dec. 31, 2021 USD ($) t T
Derivative Instruments
Discontinued cash flow hedge, nonmonetary amount | T		48,100		95,800
Reclassification | $		$ 2.4		$ (1.9)
Estimated unrealized net loss associated with cash flow hedges pertaining to fuel swap agreements expected to be reclassified to earnings from accumulated other comprehensive income loss | $			$ 9.8		$ 23.8
2022
Derivative Instruments
Fuel Swap Agreements (metric tons) | T			257,950		821,850
Percentage of projected requirements			64.00%		54.00%
2022 | Not Designated as Hedging Instrument
Derivative Instruments
Discontinued cash flow hedge, nonmonetary amount			47,191
Fuel Swap Agreements (metric tons)	[1]		94,382		231,900
Notional amount since inception			47,191
2023
Derivative Instruments
Fuel Swap Agreements (metric tons) | T			743,601		249,050
Percentage of projected requirements			45.00%		15.00%
2023 | Not Designated as Hedging Instrument
Derivative Instruments
Fuel Swap Agreements (metric tons)			0		0

[1] As of September 30, 2022, 47,191 metric tons relate to fuel swap agreements with discontinued hedge accounting, in which we effectively pay fixed prices and receive floating prices from the counterparty. The remaining 47,191 metric tons relate to fuel swap agreements that were not designated as hedges since inception, in which we effectively pay floating prices and receive fixed prices from the counterparty.