Vessel Acquisitions and Dispositions (Details 1) (Thomas Wainwright [Member], Americas [Member], Platform Supply Vessel [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 hp DWT ft
Thomas Wainwright [Member] | Americas [Member] | Platform Supply Vessel [Member]
Vessels Dispositions
Year Built	2010
Length (feet)	242
Breakhorse Power	4,200
Deadweight Tons	2,700
Cost	$ 22.5