REPORTABLE SEGMENTS (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) segment	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Segment results
Number of segments | segment	2
Total Operating Revenue	$ 704.8	$ 1,165.5
Total Operating Income	38.7	432.6
Interest income	8.2
Interest expense	(4.5)	(4.8)
Other income (expense), net	1.8	2.0
Income before Taxes	44.2	429.8
Income taxes	(10.2)	(90.6)
Net Income	34.0	339.2
Deferred dry-docking amortization	6.2	6.7
Total Assets	4,227.3		$ 4,330.0
(Loss) Income from SSAT	(1.8)	34.0
SSAT
Segment results
(Loss) Income from SSAT	(1.8)	34.0
Intersegment Eliminations
Segment results
Total Operating Revenue	40.1	73.2
Ocean Transportation
Segment results
Total Operating Revenue	551.0	943.9
Total Operating Income	27.8	416.2
(Loss) Income from SSAT	(1.8)	34.0
Ocean Transportation | Intersegment Eliminations
Segment results
Total Operating Revenue	16.1	21.8
Logistics
Segment results
Total Operating Revenue	153.8	221.6
Total Operating Income	10.9	16.4
Logistics | Intersegment Eliminations
Segment results
Total Operating Revenue	$ 24.0	$ 51.4