GOODWILL AND INTANGIBLE ASSETS - GOODWILL (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Goodwill [Line Items]
Total Goodwill	$ 327.8	$ 327.8
Ocean Transportation
Goodwill [Line Items]
Total Goodwill	222.6
Ocean Transportation | Horizon
Goodwill [Line Items]
Total Goodwill	221.8
Logistics
Goodwill [Line Items]
Total Goodwill	105.2
Logistics | Span Alaska
Goodwill [Line Items]
Total Goodwill	78.6
Logistics | Other Acquisitions
Goodwill [Line Items]
Total Goodwill	$ 26.6