Commitments And Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended		0 Months Ended			12 Months Ended	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Mar. 31, 2012	Jun. 08, 2011 Robins Case [Member] claim	Apr. 20, 2011 Robins Case [Member] claim	Jul. 20, 2010 Wunstell Action [Member] plaintiff	Dec. 31, 2011 Multi-district Litigation [Member] claim	Sep. 30, 2012 Prejean [Member] claim	Mar. 28, 2012 Prejean [Member] plaintiff	Sep. 30, 2012 Offshore Support Vessels [Member] equipment	Mar. 31, 2012 Offshore Support Vessels [Member]	Mar. 31, 2012 Jack-Up Drilling Rig [Member]	Sep. 30, 2012 Helicopters [Member] equipment	Sep. 30, 2012 Inland River Liquid Tank Barges [Member] equipment	Mar. 31, 2012 Inland River Liquid Tank Barges [Member]	Mar. 31, 2012 Liquid Tank Barges Member	Sep. 30, 2012 Harbor Tugs [Member] equipment	Mar. 31, 2012 Harbor Tugs [Member]	Mar. 31, 2012 Other Machinery and Equipment [Member]	Sep. 30, 2012 Inland River Towboats [Member] equipment	Mar. 31, 2012 Inland River Towboats [Member]	Sep. 30, 2012 Capital Lease Obligations [Member] Harbor Tugs [Member] equipment
Loss Contingencies [Line Items]
Total unfunded capital commitments	$ 365.0										$ 131.4	$ 30.3			$ 138.3	$ 15.1		$ 23.0	$ 14.9		$ 9.4	$ 2.6
Unrecorded Unconditional Purchase Obligation, Maximum Quantity										12			12	7			4			3		2
Description of Guarantees Given by Parent Company	0.2
Purchase commitments payable during the period	58.6
Potential reduction amount of liability			125.0
Liquidated amount liability			3.3
Number of claims					66
Number of claims company did not attempt to dismiss				1
Number of plantiffs						2			5
Additional individual civil actions filed							5	4
Tax assessment levied		25.7
Proposed tax penalties	19.3
Proposed Tax Penalties, Maximum Exposure	$ 1.0