QUARTERLY INFORMATION (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly information by segments
Revenue	$ 443.5	$ 441.8	$ 436.4	$ 392.5	$ 410.9	$ 415.0	$ 416.6	$ 394.7	$ 1,714.2	$ 1,637.2	$ 1,560.0
Operating income	49.4	45.0	35.7	9.9	17.9	27.2	36.5	18.7	140.0	100.3	96.7
Interest expense	(4.3)	(4.4)	(4.5)	(4.1)	(3.5)	(3.6)	(3.6)	(3.7)	(17.3)	(14.4)	(11.7)
Income from Continuing Operations Before Income Taxes	45.1	40.6	31.2	5.8	14.4	23.6	32.9	15.0	122.7	85.9	85.0
Income tax expense	(17.3)	(19.1)	(13.1)	(2.4)	(7.1)	(6.4)	(12.8)	(5.9)	(51.9)	(32.2)	(33.0)
Income (Loss) from Continuing Operations Attributable to Parent, Total									70.8	53.7	52.0
Net Income (Loss) from Discontinued Operations Net of Income taxes									0	0	(6.1)
Net Income	27.8	21.5	18.1	3.4	7.3	17.2	20.1	9.1	70.8	53.7	45.9
Income From Continuing Operations, Earnings Per Share:
Basic (in dollars per share)	$ 0.65	$ 0.50	$ 0.42	$ 0.08	$ 0.17	$ 0.40	$ 0.47	$ 0.21	$ 1.65	$ 1.26	$ 1.23
Diluted (in dollars per share)	$ 0.63	$ 0.50	$ 0.42	$ 0.08	$ 0.17	$ 0.40	$ 0.47	$ 0.21	$ 1.63	$ 1.25	$ 1.22
Net Income, Earnings Per Share:
Basic (in dollars per share)									$ 1.65	$ 1.26	$ 1.09
Diluted (in dollars per share)									$ 1.63	$ 1.25	$ 1.08
Ocean Transportation
Quarterly information by segments
Revenue	333.2	329.5	321.1	294.6	309.4	310.1	310.0	299.9	1,278.4	1,229.4	1,189.8
Operating income	46.3	42.6	32.8	9.4	16.0	25.5	34.3	18.5	131.1	94.3	96.6
Logistics
Quarterly information by segments
Revenue	110.3	112.3	115.3	97.9	101.5	104.9	106.6	94.8	435.8	407.8	370.2
Operating income	$ 3.1	$ 2.4	$ 2.9	$ 0.5	$ 1.9	$ 1.7	$ 2.2	$ 0.2	$ 8.9	$ 6.0	$ 0.1