Alternative Fuel Excise Tax Credit (Details) - $ / gal	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Alternative Fuel Excise Tax Credit
Federal alternative fuels tax credit - CNG (in dollars per gasoline gallon equivalent)	0.50	0.50
Federal alternative fuels tax credit - LNG (in dollars per liquid gallon)	0.50	0.50