Consolidated Statements of Income - USD ($) shares in Thousands, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating Revenues
Total operating revenues		$ 2,379.6	$ 3,800.4	$ 5,564.4	$ 6,916.8
Operating Expenses
Depreciation and amortization		39.5	36.5	78.9	76.2
Selling, general and administrative		37.1	35.1	76.3	69.7
Accretion of asset retirement obligations		0.5	0.5	1.1	1.0
Total operating expenses		2,145.4	3,744.7	5,199.5	6,842.5
Net settlement proceeds		0.0	0.0	0.0	0.1
Gain (loss) on sale of assets		1.3	0.0	1.4	(0.1)
Income (loss) from operations		235.5	55.7	366.3	74.3
Other income (expense)
Interest income		0.2	0.9	1.0	1.6
Interest expense		(13.0)	(13.2)	(26.3)	(26.8)
Other nonoperating income (expense)		0.3	(0.1)	(0.7)	0.1
Total other income (expense)		(12.5)	(12.4)	(26.0)	(25.1)
Income (loss) before income taxes		223.0	43.3	340.3	49.2
Income tax expense (benefit)		54.1	10.6	82.1	11.2
Net Income		$ 168.9	$ 32.7	$ 258.2	$ 38.0
Basic and Diluted Earnings Per Common Share
Basic (in dollars per share)		$ 5.79	$ 1.02	$ 8.69	$ 1.18
Diluted (in dollars per share)		$ 5.73	$ 1.01	$ 8.60	$ 1.18
Weighted-Average Common Shares Outstanding (in thousands):
Basic (in shares)		29,181	32,112	29,708	32,159
Diluted (in shares)		29,495	32,328	30,018	32,372
Supplemental information:
Excise taxes		$ 380.3	$ 498.3	$ 853.7	$ 953.6
Product
Operating Revenues
Total operating revenues	[1]	1,588.9	3,129.7	4,069.1	5,629.5
Operating Expenses
Operating expenses	[1]	1,287.8	2,973.7	3,547.6	5,355.2
Merchandise sales
Operating Revenues
Total operating revenues		767.1	658.8	1,454.6	1,265.0
Operating Expenses
Operating expenses		648.7	553.3	1,228.7	1,062.0
Other operating revenues
Operating Revenues
Total operating revenues		23.6	11.9	40.7	22.3
Operating Expenses
Operating expenses		$ 131.8	$ 145.6	$ 266.9	$ 278.4

[1] Includes excise taxes of $853.7 million for the three months ended June 30, 2020, $498.3 million for the three months ended June 30, 2019, $473.5 million for the six months ended June 30, 2020 and $953.6 million the six months ended June 30, 2019.