Dispositions (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended		9 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2012 item	Mar. 31, 2012	Sep. 30, 2012	Sep. 30, 2011 item
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill		$ 9,740,000
Repayment Of Us Government Guaranteed Long Term Financing Connected To Disposition					12,500,000
Make Whole Premiums Connected To Dispositions					4,000,000
Written Off Unamortized Loan Costs Connected To Repayments Of Make Whole Premiums					700,000
Assets of Disposal Group, Including Discontinued Operation, Noncurrent		183,837,000
Derrick Barge [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds received					44,500,000
Pre-tax gain loss after sale					3,100,000
Goodwill					9,700,000
Liftboats [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds received					138,600,000	22,300,000
Pre-tax gain loss after sale	10,000,000	46,100,000		56,100,000		8,600,000
Quantity of liftboats sold			18			7
Repayment Of Us Government Guaranteed Long Term Financing Connected To Disposition					12,500,000
Make Whole Premiums Connected To Dispositions					4,000,000
Written Off Unamortized Loan Costs Connected To Repayments Of Make Whole Premiums					700,000
Loss on sale of assets, disposal group accounted for as discontinued operations	3,600,000
Costs Related To Disposition	$ 6,400,000