Condensed Consolidated Statements of Income and Comprehensive Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Operating Revenue:
Ocean transportation	$ 329.5	$ 310.1	$ 945.2	$ 920.0
Logistics	112.3	104.9	325.5	306.3
Total operating revenue	441.8	415.0	1,270.7	1,226.3
Costs and Expenses:
Operating costs	363.8	353.6	1,078.5	1,041.3
Equity in (income) loss of terminal joint venture	(3.1)	2.4	(5.4)	3.0
Selling, general and administrative	36.1	31.8	107.0	99.6
Total costs and expenses	396.8	387.8	1,180.1	1,143.9
Operating Income	45.0	27.2	90.6	82.4
Interest expense	(4.4)	(3.6)	(13.0)	(10.9)
Income before income taxes	40.6	23.6	77.6	71.5
Income tax expense	(19.1)	(6.4)	(34.6)	(25.1)
Net Income	21.5	17.2	43.0	46.4
Other Comprehensive Income (Loss), Net of Income Taxes:
Net Income	21.5	17.2	43.0	46.4
Other Comprehensive Income (Loss):
Net gain (loss) and prior service cost				(0.8)
Amortization of prior service cost included in net periodic pension cost	(0.3)	(0.3)	(0.8)	(1.0)
Amortization of net loss included in net periodic pension cost	0.7	1.2	2.1	3.5
Foreign currency translation adjustment	0.3	0.1	0.2	(0.1)
Total Other Comprehensive Income	0.7	1.0	1.5	1.6
Comprehensive Income	$ 22.2	$ 18.2	$ 44.5	$ 48.0
Basic Earnings Per Share (in dollars per share)	$ 0.50	$ 0.40	$ 1.00	$ 1.09
Diluted Earnings Per Share (in dollars per share)	$ 0.50	$ 0.40	$ 1.00	$ 1.08
Weighted Average Number of Shares Outstanding:
Basic (in shares)	43.0	42.8	43.0	42.7
Diluted (in shares)	43.4	43.3	43.3	43.1