Segment Results: (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment results
Revenue	$ 415.0	$ 401.4	$ 1,226.3	$ 1,161.7
Operating income	27.2	34.2	82.4	72.8
Interest Expense	(3.6)	(4.0)	(10.9)	(7.9)
Income from Continuing Operations Before Income Taxes	23.6	30.2	71.5	64.9
Income Tax Expense	(6.4)	(11.2)	(25.1)	(28.6)
Income From Continuing Operations	17.2	19.0	46.4	36.3
Loss From Discontinued Operations (net of income taxes)		0.1		(6.0)
Net Income	17.2	19.1	46.4	30.3
Ocean Transportation
Segment results
Revenue	310.1	307.1	920.0	886.1
Operating income	25.5	32.9	78.3	69.9
Logistics
Segment results
Revenue	104.9	94.3	306.3	275.6
Operating income	$ 1.7	$ 1.3	$ 4.1	$ 2.9