Condensed Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Operating Revenue:
Total Operating Revenue	$ 827.5	$ 1,114.8	$ 2,305.7	$ 3,541.4
Costs and Expenses:
Operating costs	(624.1)	(738.4)	(1,826.3)	(2,170.5)
Income (Loss) from SSAT	1.3	23.4	(1.9)	82.1
Selling, general and administrative	(72.6)	(64.5)	(210.0)	(192.0)
Total Costs and Expenses	(695.4)	(779.5)	(2,038.2)	(2,280.4)
Operating Income	132.1	335.3	267.5	1,261.0
Interest income	9.3	1.3	26.2	1.3
Interest expense	(2.4)	(5.0)	(9.8)	(14.3)
Other income (expense), net	1.2	2.5	4.8	6.3
Income before Taxes	140.2	334.1	288.7	1,254.3
Income taxes	(20.3)	(68.1)	(54.0)	(268.4)
Net Income	119.9	266.0	234.7	985.9
Other Comprehensive Income (Loss), Net of Income Taxes:
Net Income (Loss)	119.9	266.0	234.7	985.9
Other Comprehensive Income (Loss):
Net change in pension and post-retirement liabilities	(0.8)	(0.7)	(2.5)	0.3
Other adjustments	(0.6)	(1.9)	0.1	(3.5)
Total Other Comprehensive Income (Loss), Net of Income Taxes	(1.4)	(2.6)	(2.4)	(3.2)
Comprehensive Income	$ 118.5	$ 263.4	$ 232.3	$ 982.7
Basic Earnings Per Share (in dollars per share)	$ 3.42	$ 6.95	$ 6.59	$ 24.83
Diluted Earnings Per Share (in dollars per share)	$ 3.40	$ 6.89	$ 6.56	$ 24.65
Weighted Average Number of Shares Outstanding:
Basic (in shares)	35.1	38.3	35.6	39.7
Diluted (in shares)	35.3	38.6	35.8	40.0
Ocean. Transportation.
Operating Revenue:
Total Operating Revenue	$ 669.4	$ 918.5	$ 1,837.3	$ 2,911.6
Logistics.
Operating Revenue:
Total Operating Revenue	$ 158.1	$ 196.3	$ 468.4	$ 629.8