Vessel Acquisitions and Dispositions (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended			3 Months Ended	1 Months Ended			3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	May 03, 2012 Vessel	Sep. 30, 2011 North Sea [Member] Shipyard Vessel	Apr. 30, 2012 U.S Gulf of Mexico [Member] Vessel	May 31, 2012 Americas [Member] Vessel	Jan. 31, 2012 Americas [Member] Vessel	Sep. 30, 2011 Simek [Member] Vessel
Vessel Acquisitions and Dispositions (Textual) [Abstract]
Number of vessels of purchased							1
Number of vessel sold						2	1
Gain on sale of Vessels						$ 4.2	$ 1.2
Purchase price of vessels							22.5
Number of vessels expected to operate				6	2
Number of vessels under construction								1
Estimated cost of additional vessel								60.9
Estimated cost of building vessels				245.0	73.0
Number of shipyards use in agreements				3
Additional Vessel Acquisitions and Dispositions (Textual) [Abstract]
Number of vessels being held for sale but not included in fleets			1
Capitalized interest on Vessels and Equipment	$ 0.7	$ 0