Condensed Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating Revenue:
Ocean Transportation	$ 444.8	$ 329.5	$ 1,097.0	$ 945.2
Logistics	99.5	112.3	293.1	325.5
Total Operating Revenue	544.3	441.8	1,390.1	1,270.7
Costs and Expenses:
Operating costs	424.8	363.8	1,107.5	1,078.5
Equity in income of terminal joint venture	(4.5)	(3.1)	(13.1)	(5.4)
Selling, general and administrative	52.2	36.1	145.3	107.0
Total Costs and Expenses	472.5	396.8	1,239.7	1,180.1
Operating Income	71.8	45.0	150.4	90.6
Interest expense	(4.7)	(4.4)	(13.6)	(13.0)
Income before Income Taxes	67.1	40.6	136.8	77.6
Income tax expense	(25.6)	(19.1)	(60.4)	(34.6)
Net Income	41.5	21.5	76.4	43.0
Other Comprehensive Income (Loss), Net of Income Taxes:
Net Income	41.5	21.5	76.4	43.0
Other Comprehensive Income (Loss):
Net loss in prior service cost			(0.2)
Amortization of prior service cost included in net periodic pension cost	(0.4)	(0.3)	(1.0)	(0.8)
Amortization of net gain included in net periodic pension cost	1.2	0.7	3.5	2.1
Foreign currency translation adjustment	0.8	0.3	1.5	0.2
Total Other Comprehensive Income	1.6	0.7	3.8	1.5
Comprehensive Income	$ 43.1	$ 22.2	$ 80.2	$ 44.5
Basic Earnings Per Share:
Basic Earnings Per Share (in dollars per share)	$ 0.95	$ 0.50	$ 1.76	$ 1.00
Diluted Earnings Per Share:
Diluted Earnings Per Share (in dollars per share)	$ 0.94	$ 0.50	$ 1.74	$ 1.00
Weighted Average Number of Shares Outstanding:
Basic (in shares)	43.5	43.0	43.5	43.0
Diluted (in shares)	44.0	43.4	44.0	43.3
Dividends:
Cash Dividends Per Share (in dollars per share)	$ 0.18	$ 0.17	$ 0.52	$ 0.49