Acquisitions (Narrative) (Details) (USD $)	12 Months Ended	1 Months Ended	12 Months Ended	0 Months Ended
	Dec. 31, 2012	Nov. 30, 2012	Dec. 31, 2014 T	Aug. 06, 2012	Jul. 31, 2013	Dec. 31, 2006 item	Mar. 31, 2013
Business Acquisition [Line Items]
Subsidiary ownership interest acquired					23.68%
Cash payment included in purchase price	$ 620,000
Number of Vessels Owned or Operated						2
United Ocean Services, LLC [Member]
Business Acquisition [Line Items]
Acquisition date			Nov. 30, 2012
Subsidiary ownership interest acquired		100.00%
Amount of total consideration		114,700,000
Cash payment included in purchase price		112,200,000
Post-closing settlement payment							2,500,000
Acquisition expenses	1,800,000
Weight of U.S. Flag Jones Act dry bulk fleet			131,000
Frascati Shops, Inc. And Tower, LLC [Member]
Business Acquisition [Line Items]
Acquisition date			Aug. 06, 2012
Amount of total consideration				4,500,000
Cash payment included in purchase price				600,000
Debt assumed				3,500,000
Assumption of miscellaneous payables				400,000
Acquisition expenses				$ 40,000
Handysize Bulk Carriers [Member] | United Ocean Services, LLC [Member]
Business Acquisition [Line Items]
Number of Vessels Owned or Operated			2
Tug And Barge Units [Member] | United Ocean Services, LLC [Member]
Business Acquisition [Line Items]
Number of Vessels Owned or Operated			4