Revenue (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 2,805	$ 4,331	$ 8,157	$ 12,498
Motor Fuel Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,711	4,225	7,869	12,174
Lease Income [Member]
Disaggregation of Revenue [Line Items]
Revenues	34	37	103	107
Fuel Distribution and Marketing [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,644	4,086	7,703	11,819
Fuel Distribution and Marketing [Member] | Dealer Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	586	928	1,621	2,695
Fuel Distribution and Marketing [Member] | Distributor Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,316	2,027	3,428	5,808
Fuel Distribution and Marketing [Member] | Unbranded Wholesale Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	426	667	1,569	1,940
Fuel Distribution and Marketing [Member] | Commission Agent Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues	272	419	951	1,233
Fuel Distribution and Marketing [Member] | Non Motor Fuel [Member]
Disaggregation of Revenue [Line Items]
Revenues	14	14	45	49
Fuel Distribution and Marketing [Member] | Lease Income [Member]
Disaggregation of Revenue [Line Items]
Revenues	30	31	89	94
All Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	161	245	454	679
All Other [Member] | Motor Fuel Sales [Member]
Disaggregation of Revenue [Line Items]
Revenues	111	184	300	498
All Other [Member] | Non Motor Fuel [Member]
Disaggregation of Revenue [Line Items]
Revenues	46	55	140	168
All Other [Member] | Lease Income [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 4	$ 6	$ 14	$ 13