GOODWILL AND INTANGIBLES - CHANGES IN GOODWILL (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Goodwill [Line Items]
Balance at the beginning of the period	$ 323.7	$ 323.7	$ 323.7	$ 245.1	$ 241.6	$ 241.6
Additions	0.0	0.0	0.0	79.0	3.5	0.0
Balance at the end of the period	323.7	323.7	323.7	324.1	245.1	241.6
Ocean Transportation
Goodwill [Line Items]
Balance at the beginning of the period	218.5	218.5	218.5	218.5	215.0	215.0
Additions	0.0	0.0	0.0	0.0	3.5	0.0
Balance at the end of the period	218.5	218.5	218.5	218.5	218.5	215.0
Logistics
Goodwill [Line Items]
Balance at the beginning of the period	105.2	105.2	105.2	26.6	26.6	26.6
Additions	0.0	0.0	0.0	79.0	0.0	0.0
Balance at the end of the period	$ 105.2	$ 105.2	$ 105.2	$ 105.6	$ 26.6	$ 26.6