Condensed Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating Revenue:
Ocean Transportation	$ 370.9	$ 346.7	$ 737.0	$ 652.2
Logistics	96.8	100.9	184.9	193.6
Total Operating Revenue	467.7	447.6	921.9	845.8
Costs and Expenses:
Operating costs	389.9	364.5	766.3	682.7
Equity in income of related party Terminal Joint Venture	(3.0)	(5.2)	(5.6)	(8.6)
Selling, general and administrative	44.7	54.6	90.5	93.1
Total Costs and Expenses	431.6	413.9	851.2	767.2
Operating Income	36.1	33.7	70.7	78.6
Interest expense	(6.5)	(4.6)	(11.4)	(8.9)
Income before Income Taxes	29.6	29.1	59.3	69.7
Income tax expense	(11.6)	(19.2)	(23.2)	(34.8)
Net Income	18.0	9.9	36.1	34.9
Other Comprehensive Income (Loss), Net of Income Taxes:
Net Income	18.0	9.9	36.1	34.9
Other Comprehensive Income (Loss):
Net gain (loss) in prior service cost			0.7	(0.2)
Amortization of prior service cost included in net periodic pension cost	(0.2)	(0.2)	(0.6)	(0.6)
Amortization of net loss included in net periodic pension cost	1.0	0.9	2.1	2.3
Foreign currency translation adjustment		0.6	(0.1)	0.7
Total Other Comprehensive Income	0.8	1.3	2.1	2.2
Comprehensive Income	$ 18.8	$ 11.2	$ 38.2	$ 37.1
Basic Earnings Per-Share:
Basic Earnings Per-Share (in dollars per share)	$ 0.42	$ 0.23	$ 0.83	$ 0.80
Diluted Earnings Per-Share:
Diluted Earnings Per-Share (in dollars per share)	$ 0.42	$ 0.23	$ 0.83	$ 0.79
Weighted Average Number of Shares Outstanding:
Basic (in shares)	43.1	43.5	43.3	43.4
Diluted (in shares)	43.4	44.0	43.7	43.9
Dividends
Cash Dividends Per-Share	$ 0.18	$ 0.17	$ 0.36	$ 0.34