Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating Revenue:
Total Operating Revenue	$ 4,343.0	$ 3,925.3	$ 2,383.3
Costs and Expenses:
Operating costs	(2,811.5)	(2,557.6)	(1,904.3)
Income from SSAT	83.1	56.3	26.3
Selling, general and administrative	(261.0)	(236.5)	(225.0)
Total Costs and Expenses	(2,989.4)	(2,737.8)	(2,103.0)
Operating Income	1,353.6	1,187.5	280.3
Interest income	8.2
Interest expense	(18.0)	(22.6)	(27.4)
Other income (expense), net	8.5	6.4	6.1
Income before Taxes	1,352.3	1,171.3	259.0
Income taxes	(288.4)	(243.9)	(65.9)
Net Income	1,063.9	927.4	193.1
Other Comprehensive Income (Loss), Net of Income Taxes:
Net Income	1,063.9	927.4	193.1
Other Comprehensive Income (Loss):
Amortization of prior service cost	(3.5)	(4.6)	(4.7)
Amortization of net loss (gain)	27.3	25.0	(9.4)
Other adjustments	0.2	(0.5)	0.2
Total Other Comprehensive Income (Loss)	24.0	19.9	(13.9)
Comprehensive Income	$ 1,087.9	$ 947.3	$ 179.2
Basic Earnings Per Share (in dollars per share)	$ 27.28	$ 21.67	$ 4.48
Diluted Earnings Per Share (in dollars per share)	$ 27.07	$ 21.47	$ 4.44
Weighted Average Number of Shares Outstanding:
Basic (in shares)	39.0	42.8	43.1
Diluted (in shares)	39.3	43.2	43.5
Ocean. Transportation.
Operating Revenue:
Total Operating Revenue	$ 3,544.6	$ 3,132.8	$ 1,853.9
Logistics.
Operating Revenue:
Total Operating Revenue	$ 798.4	$ 792.5	$ 529.4