Summary of Significant Accounting Policies - Property (Details)	12 Months Ended
	Dec. 31, 2019
Gasoline station buildings, improvements and storage tanks | Minimum
Property and Equipment
Estimated useful life	15 years
Gasoline station buildings, improvements and storage tanks | Maximum
Property and Equipment
Estimated useful life	25 years
Buildings and improvements | Minimum
Property and Equipment
Estimated useful life	5 years
Buildings and improvements | Maximum
Property and Equipment
Estimated useful life	25 years
Gasoline station equipment
Property and Equipment
Estimated useful life	7 years
Fixtures, equipment and capitalized internal use software | Minimum
Property and Equipment
Estimated useful life	3 years
Fixtures, equipment and capitalized internal use software | Maximum
Property and Equipment
Estimated useful life	7 years