Alternative Fuels Excise Tax Credit (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($) $ / gal	Dec. 31, 2019 USD ($)	Dec. 31, 2019 $ / gal
Alternative Fuels 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
Federal alternative fuels tax credit - credits recognized as revenue | $	$ 5.4	$ 47.1