Vessels (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Balance vessels and vessel improvements, Begining Balance	$ 1,789,381,046	$ 1,509,798,249
Vessel improvements	58,521	2,991,995
Delivery of newbuild vessels		368,800,779
Disposal of vessel		(22,494,172)
Depreciation expense	(75,131,914)	(69,715,805)
Balance vessels and vessel improvements, Ending Balance	$ 1,714,307,653	$ 1,789,381,046