Equipment Acquisitions, Dispositions and Depreciation and Impairment Policies (Narrative) (Details) (USD $)	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Property, Plant and Equipment [Line Items]
Payments to Acquire Property, Plant, and Equipment	$ 186,541,000	$ 127,407,000
Sales Price Of Equipment	65,600,000
Proceeds from Sale of Property, Plant and Equipment, Excluding Deposits on Future Equipment Sales	11,700,000
Proceeds from disposition of property and equipment	11,920,000	25,080,000
Payments for (Proceeds from) Other Deposits	5,000,000
Proceeds from Issuance of Secured Debt	48,900,000
Gains (Losses) on Sales of Assets	14,800,000
Deferred Gains on Asset Sales	7,300,000
Amortization Of Deferred Gains Included In Gains On Asset Dispositions And Impairments, Net	(2,455,000)	(2,461,000)
Deposits	200,000
Wind Farm Utility Vessel [Member]
Property, Plant and Equipment [Line Items]
Number Of Equipments Delivered	1
Inland River Dry Cargo Barges [Member]
Property, Plant and Equipment [Line Items]
Number Of Equipments Delivered	3
Inland River Liquid Tank Barges [Member]
Property, Plant and Equipment [Line Items]
Number Of Equipments Delivered	2
Offshore Support Vessels [Member]
Property, Plant and Equipment [Line Items]
Number Of Equipments Delivered	1
Number Of Equipments Sold	4
Helicopters [Member]
Property, Plant and Equipment [Line Items]
Number Of Equipments Delivered	13
Number Of Equipments Sold	6
Inland River Towboat [Member]
Property, Plant and Equipment [Line Items]
Number Of Equipments Delivered	1
Number Of Equipments Sold	1
Harbor And Offshore Tugs [Member]
Property, Plant and Equipment [Line Items]
Number Of Equipments Sold	2
Gains (Losses) on Sales of Assets [Member]
Property, Plant and Equipment [Line Items]
Deferred Gains on Asset Sales	7,500,000
Mexmar [Member]
Property, Plant and Equipment [Line Items]
Sales Price Of Equipment	50,000,000
Proceeds from disposition of property and equipment	$ 48,500,000
Mexmar [Member] | Offshore Support Vessels [Member]
Property, Plant and Equipment [Line Items]
Number Of Equipments Sold	2