QUARTERLY INFORMATION (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly information by segments
Revenue	$ 398.3	$ 401.4	$ 394.2	$ 366.1	$ 374.9	$ 380.6	$ 377.4	$ 329.7	$ 1,560.0	$ 1,462.6	$ 1,370.6
Operating income	23.9	34.2	32.5	6.1	11.8	30.9	29.2	6.7	96.7	78.6	125.4
Interest expense	(3.8)	(4.0)	(1.9)	(2.0)	(2.0)	(1.9)	(1.9)	(1.9)	(11.7)	(7.7)	(8.2)
Income from Continuing Operations Before Income Taxes	20.1	30.2	30.6	4.1	9.8	29.0	27.3	4.8	85.0	70.9	117.2
Income tax expense	4.4	11.2	15.3	2.1	3.1	10.6	9.6	1.8	33.0	25.1	46.7
Income From Continuing Operations	15.7	19.0	15.3	2.0	6.7	18.4	17.7	3.0	52.0	45.8	70.5
(Loss) income from discontinued operations	(0.1)	0.1	(7.5)	1.4	(5.1)	(9.7)	1.0	2.2	(6.1)	(11.6)	21.6
Net Income	15.6	19.1	7.8	3.4	1.6	8.7	18.7	5.2	45.9	34.2	92.1
Income From Continuing Operations, Earnings Per Share:
Basic (in dollars per share)	$ 0.37	$ 0.45	$ 0.36	$ 0.05	$ 0.16	$ 0.44	$ 0.42	$ 0.07	$ 1.23	$ 1.10	$ 1.71
Diluted (in dollars per share)	$ 0.37	$ 0.45	$ 0.36	$ 0.05	$ 0.16	$ 0.44	$ 0.42	$ 0.07	$ 1.22	$ 1.09	$ 1.70
Net Income, Earnings Per Share:
Basic (in dollars per share)	$ 0.37	$ 0.45	$ 0.18	$ 0.08	$ 0.04	$ 0.21	$ 0.45	$ 0.12	$ 1.09	$ 0.82	$ 2.23
Diluted (in dollars per share)	$ 0.36	$ 0.45	$ 0.18	$ 0.08	$ 0.04	$ 0.21	$ 0.44	$ 0.12	$ 1.08	$ 0.81	$ 2.22
Ocean transportation
Quarterly information by segments
Revenue	303.7	307.1	299.5	279.5	282.1	281.4	274.3	238.4	1,189.8	1,076.2	1,015.0
Operating income	26.7	32.9	31.2	5.8	12.5	28.9	27.1	5.2	96.6	73.7	118.3
Logistics services
Quarterly information by segments
Revenue	94.6	94.3	94.7	86.6	92.8	99.2	103.1	91.3	370.2	386.4	355.6
Operating income	$ (2.8)	$ 1.3	$ 1.3	$ 0.3	$ (0.7)	$ 2.0	$ 2.1	$ 1.5	$ 0.1	$ 4.9	$ 7.1