Summary of Significant Accounting Policies - Alternative Fuels Tax Credit (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 $ / gal	Dec. 31, 2020 $ / gal	Dec. 31, 2019 USD ($) $ / gal
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Federal alternative fuels tax credit - credits recognized as revenue | $			$ 47.1
Federal fuel tax credit - CNG (in dollars per gasoline gallon equivalent)	0.50	0.50	0.50
Federal fuel tax credit - LNG (in dollars per liquid gallon)	0.50	0.50	0.50