REPORTABLE SEGMENTS (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) segment	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Segment results
Number of segments | segment			2
Revenue	$ 447.6	$ 436.4	$ 845.8	$ 828.9
Operating Income	33.7	35.7	78.6	45.6
Interest expense, net	(4.6)	(4.5)	(8.9)	(8.6)
Income before Income Taxes	29.1	31.2	69.7	37.0
Income tax expense	(19.2)	(13.1)	(34.8)	(15.5)
Net Income	9.9	18.1	34.9	21.5
Assets	1,726.2		1,726.2		$ 1,401.8
Capital expenditures			12.2	20.2
Depreciation and amortization			35.6	35.2
Operating segments
Segment results
Operating Income	33.7	35.7	78.6	45.6
Ocean Transportation | Operating segments
Segment results
Revenue	346.7	321.1	652.2	615.7
Operating Income	31.4	32.8	75.3	42.2
Logistics | Operating segments
Segment results
Revenue	100.9	115.3	193.6	213.2
Operating Income	$ 2.3	$ 2.9	$ 3.3	$ 3.4