Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Revenue:
Ocean Transportation	$ 1,541.1	$ 1,498.0	$ 1,278.4
Logistics	400.5	386.9	435.8
Total Operating Revenue	1,941.6	1,884.9	1,714.2
Costs and Expenses:
Operating costs	1,619.1	1,510.1	1,433.5
Equity in income of related party Terminal Joint Venture	(15.8)	(16.5)	(6.6)
Selling, general and administrative	185.1	195.0	147.3
Total Costs and Expenses	1,788.4	1,688.6	1,574.2
Operating Income	153.2	196.3	140.0
Interest expense	(24.1)	(18.5)	(17.3)
Income before Income Taxes	129.1	177.8	122.7
Income tax expense	(48.6)	(74.8)	(51.9)
Net Income	80.5	103.0	70.8
Other Comprehensive Income (Loss), Net of Income Taxes:
Net Income	80.5	103.0	70.8
Other Comprehensive Income (Loss):
Net gain (loss) in prior service cost	0.7	5.1	(31.4)
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	1.2	1.8	2.5
Foreign currency translation and other adjustments	0.1	0.7	0.4
Other comprehensive income	0.1	0.1
Total Other Comprehensive Income (Loss)	0.8	6.4	(29.8)
Comprehensive Income	$ 81.3	$ 109.4	$ 41.0
Basic Earnings Per-Share: (in dollars per share)	$ 1.87	$ 2.37	$ 1.65
Diluted Earnings Per-Share: (in dollars per share)	$ 1.85	$ 2.34	$ 1.63
Weighted Average Number of Shares Outstanding:
Basic (in shares)	43.1	43.5	43.0
Diluted (in shares)	43.5	44.0	43.4