SIGNIFICANT ACCOUNTING POLICIES - RECOGNITION OF REVENUES AND EXPENSES (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Vessel management and related services									$ 6.8	$ 6.6	$ 6.2
Total	$ 564.9	$ 589.4	$ 557.1	$ 511.4	$ 516.1	$ 543.9	$ 512.5	$ 474.4	2,222.8	2,046.9	1,941.6
Ocean Transportation
Total	418.1	437.3	406.6	379.3	389.9	419.2	392.7	370.0
Logistics
Total	$ 146.8	$ 152.1	$ 150.5	$ 132.1	$ 126.2	$ 124.7	$ 119.8	$ 104.4
Ocean Transportation
Ocean Transportation services									1,599.3	1,531.8	1,504.5
Terminal and other related services									23.0	23.5	22.9
Fuel sales									$ 12.2	9.9	7.5
Percentage of ocean transportation revenues and fuel sales denominated in foreign currency									3.00%
Total									$ 1,641.3	1,571.8	1,541.1
Logistics
Transportation Brokerage and Freight Forwarding Services									549.1	445.1	373.7
Warehouse and distribution services									19.1	17.5	19.7
Supply chain management and other services									13.3	12.5	7.1
Total									$ 581.5	$ 475.1	$ 400.5
Percentage of transportation brokerage and freight forwarding services revenue denominated in foreign currency									3.00%