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