INVESTMENT IN SSAT (Details) - USD ($) $ in Millions		12 Months Ended
	Mar. 01, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Sep. 16, 2022
Investments in affiliates
Investment in SSAT		$ 84.1	$ 85.5
Impairment charges related to investment in SSAT		0.0	0.0	$ 0.0
Financial information for equity method investment
Company's Share of SSAT's Net Income (Loss)		(1.0)	2.2	83.1
Distributions Received		14.0		47.3
Current assets		609.6	602.3
Non-current assets		3,985.8	3,692.3
Total Assets		4,595.4	4,294.6
Current liabilities		560.4	562.3
Non-current liabilities		1,383.0	1,331.6
Total Liabilities and Shareholders' Equity		4,595.4	4,294.6
SSAT ST
Investments in affiliates
Ownership percentage, noncontrolling owner	50.00%
SSAT
Investments in affiliates
Increase in equity method investment in SSAT		13.2
Equity Method Investments, Increase (decrease) in deferred income taxes expense (benefit),		3.1
Equity method investments, increase (decrease) in retained earnings		10.1
Equity method investment decrease in investment in subsidiary				15.5
Equity method investment increase in deferred tax assets in subsidiary				3.9
Equity method investment decrease in retained earnings in subsidiary				11.6
Ocean Transportation
Financial information for equity method investment
Company's Share of SSAT's Net Income (Loss)		(1.0)	2.2	83.1
Ocean Transportation | SSAT
Financial information for equity method investment
Current assets		305.7	304.0
Non-current assets		1,625.8	1,510.2
Total Assets		1,931.5	1,814.2
Current liabilities		271.9	271.8
Non-current liabilities		1,371.5	1,255.3
Equity		288.1	287.1
Total Liabilities and Shareholders' Equity		1,931.5	1,814.2
Operating revenue		1,193.3	1,025.1	1,466.9
Operating costs and expenses		(1,162.6)	(1,019.6)	(1,168.8)
Operating income		30.7	5.5	298.1
Net (Loss) Income		(6.4)	11.9	249.6
SSAT
Investments in affiliates
Asset impairment		18.4	0.0	0.0
SSAT | Ocean Transportation
Investments in affiliates
Cost of services from transactions with unconsolidated affiliate		320.9	297.2	$ 308.3
Accounts payable and accrued liabilities		$ 34.4	$ 43.4
SSAT | SSAT ST
Investments in affiliates
Percentage of interests sold in SSAT ST	25.00%
SSAT's ownership interest in SSAT ST (as a percent)	50.00%
SSAT | SSAT Terminals Oakland
Investments in affiliates
Investment in SSAT, interest acquired (as a percent)					20.00%