Equipment Acquisitions, Dispositions and Depreciation and Impairment Policies (Useful Life) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended			0 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012 Y	Jun. 30, 2012 Offshore Support Vessels [Member] Y	Jun. 30, 2012 Wind Farm Utility Vessel [Member] Y	Jul. 01, 2011 Helicopters [Member] Y	Jun. 30, 2012 Helicopters [Member] Y		Jun. 30, 2011 Helicopters [Member] Y	Jun. 30, 2012 Inland River Dry Cargo And Deck Barges [Member] Y	Jun. 30, 2012 Inland River Liquid Tank Barges [Member] Y	Jun. 30, 2012 Inland River Towboats [Member] Y	Jun. 30, 2012 U S Flag Tankers [Member] Y	Jun. 30, 2012 R O R O Vessels [Member] Y	Jun. 30, 2012 Harbor And Offshore Tugs [Member] Y
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)		25	20	10	15	15	[1]	12	20	25	25	25	20	25
Property, Plant and Equipment, Salvage Value, Percentage					40.00%			30.00%
Increase In Operating Income From Change In Estimate	$ 4.4	$ 8.4
Increase In Net Income From Change In Estimate	$ 2.9	$ 5.4
Increase In Diluted Earnings Per Share From Change In Estimate	$ 0.14	$ 0.26

[1] Effective July 1, 2011, the Company changed its estimated useful life and salvage value for helicopters from 12 to 15 years and 30% to 40%, respectively, due to improvements in new aircraft models that continue to increase their long-term value and make them viable for operation over a longer period of time. For the three months ended June 30, 2012, the change in estimate increased operating income by $4.4 million, net income by $2.9 million, and basic and diluted earnings per share by $0.14. For the six months ended June 30, 2012, the change in estimate increased operating income by $8.4 million, net income by $5.4 million, and basic and diluted earnings per share by $0.26.