Revenues (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]
Revenue	$ 2,379.6	$ 3,800.4	$ 5,564.4	$ 6,916.8
Total petroleum product sales
Disaggregation of Revenue [Line Items]
Revenue	1,588.9	3,129.7	4,069.1	5,629.5
Petroleum product sales (at retail)
Disaggregation of Revenue [Line Items]
Revenue	1,444.8	2,818.2	3,691.0	5,056.9
Petroleum product sales (at wholesale)
Disaggregation of Revenue [Line Items]
Revenue	144.1	311.5	378.1	572.6
Merchandise sales
Disaggregation of Revenue [Line Items]
Revenue	767.1	658.8	1,454.6	1,265.0
RINs
Disaggregation of Revenue [Line Items]
Revenue	22.6	10.9	38.1	20.0
Other revenues
Disaggregation of Revenue [Line Items]
Revenue	1.0	1.0	2.6	2.3
Operating Segments | Marketing
Disaggregation of Revenue [Line Items]
Revenue	2,379.6	3,800.4	5,564.3	6,916.7
Operating Segments | Marketing | Total petroleum product sales
Disaggregation of Revenue [Line Items]
Revenue	1,588.9	3,129.7	4,069.1	5,629.5
Operating Segments | Marketing | Petroleum product sales (at retail)
Disaggregation of Revenue [Line Items]
Revenue	1,444.8	2,818.2	3,691.0	5,056.9
Operating Segments | Marketing | Petroleum product sales (at wholesale)
Disaggregation of Revenue [Line Items]
Revenue	144.1	311.5	378.1	572.6
Operating Segments | Marketing | Merchandise sales
Disaggregation of Revenue [Line Items]
Revenue	767.1	658.8	1,454.6	1,265.0
Operating Segments | Marketing | RINs
Disaggregation of Revenue [Line Items]
Revenue	22.6	10.9	38.1	20.0
Operating Segments | Marketing | Other revenues
Disaggregation of Revenue [Line Items]
Revenue	1.0	1.0	2.5	2.2
Corporate and other assets
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.1	0.1
Corporate and other assets | Total petroleum product sales
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
Corporate and other assets | Petroleum product sales (at retail)
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
Corporate and other assets | Petroleum product sales (at wholesale)
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
Corporate and other assets | Merchandise sales
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
Corporate and other assets | RINs
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
Corporate and other assets | Other revenues
Disaggregation of Revenue [Line Items]
Revenue	$ 0.0	$ 0.0	$ 0.1	$ 0.1