Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Revenue:
Ocean Transportation	$ 1,498.0	$ 1,278.4	$ 1,229.4
Logistics	386.9	435.8	407.8
Total Operating Revenue	1,884.9	1,714.2	1,637.2
Costs and Expenses:
Operating costs	1,510.1	1,433.5	1,402.3
Equity in (income) loss of related party Terminal Joint Venture	(16.5)	(6.6)	2.0
Selling, general and administrative	195.0	147.3	132.6
Total Costs and Expenses	1,688.6	1,574.2	1,536.9
Operating Income	196.3	140.0	100.3
Interest expense	(18.5)	(17.3)	(14.4)
Income before Income Taxes	177.8	122.7	85.9
Income tax expense	(74.8)	(51.9)	(32.2)
Net Income	103.0	70.8	53.7
Other Comprehensive Income (Loss), Net of Income Taxes:
Net Income	103.0	70.8	53.7
Other Comprehensive Income (Loss):
Net gain (loss) in prior service cost	5.1	(31.4)	18.7
Amortization of prior service cost included in net periodic pension cost	(1.3)	(1.3)	(1.3)
Amortization of net loss included in net periodic pension cost	1.8	2.5	4.7
Foreign currency translation adjustment	0.7	0.4	(0.1)
Other comprehensive income	0.1
Total Other Comprehensive (Loss) Income	6.4	(29.8)	22.0
Comprehensive Income	$ 109.4	$ 41.0	$ 75.7
Basic Earnings Per Share:
Basic Earnings Per Share (in dollars per share)	$ 2.37	$ 1.65	$ 1.26
Diluted Earnings Per Share:
Diluted Earnings Per Share (in dollars per share)	$ 2.34	$ 1.63	$ 1.25
Weighted Average Number of Shares Outstanding:
Basic (in shares)	43.5	43.0	42.7
Diluted (in shares)	44.0	43.4	43.1