REPORTABLE SEGMENTS (Details) (USD $) In Millions, 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 item	Dec. 31, 2011	Dec. 31, 2010
Segment results
Number of segments									2
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, net	(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
Income (Loss) From Discontinued Operations (net of income taxes)	(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
Assets	1,174.3				2,544.3				1,174.3	2,544.3	2,494.6
Capital expenditures									38.1	47.2	71.2
Depreciation and amortization									72.5	71.6	70.8
Goodwill	27.0				27.0				27.0	27.0	27.0
Discontinued Operations
Segment results
Assets					1,400.0					1,400.0	1,300.0
Reportable segments
Segment results
Assets	1,174.3				2,544.3				1,174.3	2,544.3	2,494.6
Capital expenditures									38.1	47.2	71.2
Depreciation and amortization									72.5	71.6	70.8
Ocean Transportation
Segment results
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
Assets	1,097.2				1,083.9				1,097.2	1,083.9	1,084.7
Capital expenditures									37.0	44.2	69.4
Depreciation and amortization									69.1	68.4	67.6
Ocean Transportation | SSAT
Segment results
Equity in earnings from affiliates	3.2				8.6				3.2	8.6	12.8
Equity method investments	59.6				56.5				59.6	56.5	52.9
Logistics
Segment results
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
Assets	77.1				76.4				77.1	76.4	73.8
Capital expenditures									1.1	3.0	1.8
Depreciation and amortization									3.4	3.2	3.2
Goodwill	27.0				27.0				27.0	27.0	27.0
Other
Segment results
Assets					$ 1,384.0					$ 1,384.0	$ 1,336.1