Revenue (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 2,080	$ 4,475	$ 5,352	$ 8,167
Motor Fuel Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,992	4,366	5,158	7,949
Lease Income [Member]
Disaggregation of Revenue [Line Items]
Revenues	34	35	69	70
Fuel Distribution and Marketing [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,979	4,240	5,059	7,733
Fuel Distribution and Marketing [Member] | Dealer Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	374	989	1,035	1,767
Fuel Distribution and Marketing [Member] | Distributor Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	645	2,142	2,112	3,781
Fuel Distribution and Marketing [Member] | Unbranded Wholesale Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	548	623	1,143	1,273
Fuel Distribution and Marketing [Member] | Commission Agent Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	363	439	679	814
Fuel Distribution and Marketing [Member] | Non Motor Fuel [Member]
Disaggregation of Revenue [Line Items]
Revenues	20	16	31	35
Fuel Distribution and Marketing [Member] | Lease Income [Member]
Disaggregation of Revenue [Line Items]
Revenues	29	31	59	63
All Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	101	235	293	434
All Other [Member] | Motor Fuel Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues	62	173	189	314
All Other [Member] | Non Motor Fuel [Member]
Disaggregation of Revenue [Line Items]
Revenues	34	58	94	113
All Other [Member] | Lease Income [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 5	$ 4	$ 10	$ 7