Organization and Basis of Presentation - Risk, Impairment, etc. (Details) - customer	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Sales Revenue | Product
Concentration of Risk
Percentage of consolidated total	100.00%	100.00%	100.00%	100.00%
Sales Revenue | Product | Gasoline and gasoline blendstocks
Concentration of Risk
Percentage of consolidated total	82.00%	71.00%	75.00%	65.00%
Sales Revenue | Product | Crude Oil
Concentration of Risk
Percentage of consolidated total		5.00%	1.00%	6.00%
Sales Revenue | Product | Distillates, residual oil and propane sales
Concentration of Risk
Percentage of consolidated total	14.00%	20.00%	21.00%	25.00%
Sales Revenue | Product | Station operations (convenience stores, rental and sundries)
Concentration of Risk
Percentage of consolidated total	4.00%	4.00%	3.00%	4.00%
Sales Revenue | Customer
Concentration of Risk
Number of significant customers	0	0	0	0
Product Margin [Member]
Concentration of Risk
Percentage of consolidated total	100.00%	100.00%	100.00%	100.00%
Product Margin [Member] | Wholesale Segment
Concentration of Risk
Percentage of consolidated total	2.00%	21.00%	18.00%	24.00%
Product Margin [Member] | Gasoline Distribution and Station Operations Segment
Concentration of Risk
Percentage of consolidated total	95.00%	76.00%	79.00%	73.00%
Product Margin [Member] | Commercial Segment
Concentration of Risk
Percentage of consolidated total	3.00%	3.00%	3.00%	3.00%