Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Revenue:
Total Operating Revenue	$ 2,383.3	$ 2,203.1	$ 2,222.8
Costs and Expenses:
Operating costs	(1,904.3)	(1,878.0)	(1,875.0)
Income from SSAT	26.3	20.8	36.8
Selling, general and administrative	(225.0)	(216.8)	(220.8)
Total Costs and Expenses	(2,103.0)	(2,074.0)	(2,059.0)
Operating Income	280.3	129.1	163.8
Interest expense	(27.4)	(22.5)	(18.7)
Other income (expense), net	6.1	1.2	2.6
Income before Income Taxes	259.0	107.8	147.7
Income taxes	(65.9)	(25.1)	(38.7)
Net Income	193.1	82.7	109.0
Other Comprehensive Income (Loss), Net of Income Taxes:
Net Income	193.1	82.7	109.0
Other Comprehensive Income (Loss):
Amortization of prior service cost	(4.7)	(4.5)	(4.7)
Amortization of net loss (gain)	(9.4)	2.7	1.1
Other adjustments	0.2	(0.6)
Total Other Comprehensive Income (Loss)	(13.9)	(2.4)	(3.6)
Comprehensive Income	$ 179.2	$ 80.3	$ 105.4
Basic Earnings Per-Share: (in dollars per share)	$ 4.48	$ 1.93	$ 2.55
Diluted Earnings Per-Share: (in dollars per share)	$ 4.44	$ 1.91	$ 2.53
Weighted Average Number of Shares Outstanding:
Basic	43.1	42.8	42.7
Diluted	43.5	43.3	43.0
Ocean Transportation
Operating Revenue:
Total Operating Revenue	$ 1,853.9	$ 1,666.6	$ 1,641.3
Logistics
Operating Revenue:
Total Operating Revenue	$ 529.4	$ 536.5	$ 581.5