REPORTABLE SEGMENTS (Details) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Jun. 30, 2022 USD ($) segment	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment results
Number of segments | segment					2
Total Operating Revenue	$ 1,261.1		$ 874.9		$ 2,426.6	$ 1,586.7
Operating Income	493.1		213.9		925.7	334.1
Interest expense, net	(4.5)		(5.5)		(9.3)	(12.8)
Other income (expense), net	1.8		1.5		3.8	2.9
Income before Taxes	490.4		209.9		920.2	324.2
Income taxes	(109.7)		(47.4)		(200.3)	(74.5)
Net Income	380.7	$ 339.2	162.5	$ 87.2	719.9	249.7
Deferred dry-docking amortization					12.9	12.6
Assets	4,158.6				4,158.6		$ 3,693.1
Income from SSAT	24.7		12.8		58.7	22.0
Intersegment Eliminations
Segment results
Total Operating Revenue	69.2		49.0		142.4	82.7
Ocean Transportation
Segment results
Total Operating Revenue	1,049.2		682.9		1,993.1	1,243.4
Operating Income	470.0		201.0		886.2	315.1
Income from SSAT	24.7		12.8		58.7	22.0
Ocean Transportation | Intersegment Eliminations
Segment results
Total Operating Revenue	24.0		18.7		45.8	33.8
Logistics
Segment results
Total Operating Revenue	211.9		192.0		433.5	343.3
Operating Income	23.1		12.9		39.5	19.0
Logistics | Intersegment Eliminations
Segment results
Total Operating Revenue	$ 45.2		$ 30.3		$ 96.6	$ 48.9