Property Plant and Equipment (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment [Abstract]
Depreciation and amortization under capital leases	$ 12,500,000	$ 9,400,000	$ 15,700,000
Write-down of marine equipment	$ 5,928,000	$ 0	$ 0