SIGNIFICANT ACCOUNTING POLICIES - REVENUES AND EXPENES (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total	$ 1,571.8	$ 1,541.1	$ 1,498.0
Total	475.1	400.5	386.9
Ocean Transportation
Ocean transportation services	1,531.8	1,504.5	1,472.0
Terminal and other related services	23.5	22.9	15.9
Ship management services	9.9	7.5	10.1
Fuel Sales Revenue	6.6	6.2
Total	$ 1,571.8	1,541.1	1,498.0
Percentage of ocean transportation revenues and fuel sales denominated in foreign currency	3.00%
Logistics
Transportation brokerage and freight forwarding services	$ 445.1	373.7	360.7
Warehouse and distribution services	17.5	19.7	19.8
Supply chain management and other services	12.5	7.1	6.4
Total	$ 475.1	$ 400.5	$ 386.9
Percentage of transportation brokerage and freight forwarding services revenue denominated in forgeign currency	3.00%