REPORTABLE SEGMENTS (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segment	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Segment results
Number of segments | segment			2
Revenue	$ 544.3	$ 441.8	$ 1,390.1	$ 1,270.7
Operating Income	71.8	45.0	150.4	90.6
Interest expense, net	(4.7)	(4.4)	(13.6)	(13.0)
Income before Income Taxes	67.1	40.6	136.8	77.6
Income tax expense	(25.6)	(19.1)	(60.4)	(34.6)
Net Income	41.5	21.5	76.4	43.0
Assets	1,736.7		1,736.7		$ 1,401.8
Capital expenditures			30.3	25.6
Depreciation and amortization			59.1	52.5
Operating segments
Segment results
Operating Income	71.8	45.0	150.4	90.6
Ocean Transportation | Operating segments
Segment results
Revenue	444.8	329.5	1,097.0	945.2
Operating Income	68.9	42.6	144.2	84.8
Logistics | Operating segments
Segment results
Revenue	99.5	112.3	293.1	325.5
Operating Income	$ 2.9	$ 2.4	$ 6.2	$ 5.8