LONG-TERM DEBT (Schedule of Long-term Debt) (Details)	3 Months Ended		6 Months Ended							0 Months Ended				3 Months Ended										19 Months Ended	22 Months Ended					19 Months Ended	22 Months Ended			19 Months Ended	22 Months Ended											3 Months Ended	6 Months Ended				3 Months Ended	6 Months Ended				6 Months Ended			0 Months Ended	3 Months Ended				6 Months Ended
	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Mar. 31, 2012 USD ($)	Sep. 30, 2012 Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member]	Mar. 31, 2012 Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member]	Sep. 30, 2012 Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian engine loan [Member]	Mar. 31, 2012 Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian engine loan [Member]	Dec. 01, 2011 Grand River Navigation Company, Inc. [Member] Loans payable [Member] US term loan [Member] USD ($)	Sep. 30, 2012 Grand River Navigation Company, Inc. [Member] Loans payable [Member] US term loan [Member]	Mar. 31, 2012 Grand River Navigation Company, Inc. [Member] Loans payable [Member] US term loan [Member]	Sep. 30, 2012 Grand River Navigation Company, Inc. [Member] Loans payable [Member] US term loan [Member] LIBOR [Member]	Jun. 30, 2012 Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] USD ($)	Sep. 30, 2012 Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member]	Mar. 31, 2012 Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member]	Feb. 11, 2011 Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] USD ($)	Jun. 30, 2012 Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] LIBOR [Member]	Jun. 30, 2012 Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] US Base Rate [Member]	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] Canadian Prime Rate [Member]	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] Canadian BA Rate [Member]	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] LIBOR [Member]	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] US Base Rate [Member]	Jun. 30, 2016 Third Amended & Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member] CAD	Sep. 30, 2014 Third Amended & Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member] CAD	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member] USD ($)	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member] Canadian Prime Rate [Member]	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member] Canadian BA Rate [Member]	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian engine loan [Member] USD ($)	Jun. 30, 2016 Third Amended & Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] US term loan [Member] USD ($)	Sep. 30, 2014 Third Amended & Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] US term loan [Member] USD ($)	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] Grand River Navigation Company, Inc. [Member] Loans payable [Member] US term loan [Member] USD ($)	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] Grand River Navigation Company, Inc. [Member] Loans payable [Member] US term loan [Member] US Base Rate [Member]	Jun. 30, 2016 Third Amended & Restated Credit Agreement [Member] Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] USD ($)	Sep. 30, 2014 Third Amended & Restated Credit Agreement [Member] Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] USD ($)	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] USD ($)	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] LIBOR [Member]	Sep. 30, 2012 Third Amended & Restated Credit Agreement [Member] Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] US Base Rate [Member]	Sep. 30, 2012 Second Amended and Restated Credit Agreement [Member] Canadian Prime Rate [Member]	Sep. 30, 2012 Second Amended and Restated Credit Agreement [Member] LIBOR [Member]	Sep. 30, 2012 Second Amended and Restated Credit Agreement [Member] US Base Rate [Member]	Jun. 30, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Canadian Prime Rate [Member]	Jun. 30, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Canadian BA Rate [Member]	Jun. 30, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Canadian engine loan [Member] Canadian Prime Rate [Member]	Jun. 30, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Canadian engine loan [Member] Canadian BA Rate [Member]	Jun. 30, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member] CAD	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member] CAD	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member] USD ($)	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member] Canadian Prime Rate [Member]	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian term loan [Member] Canadian BA Rate [Member]	Jun. 30, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian engine loan [Member] CAD	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian engine loan [Member] CAD	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian engine loan [Member] USD ($)	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian engine loan [Member] Canadian Prime Rate [Member]	Sep. 30, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] Canadian engine loan [Member] Canadian BA Rate [Member]	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Loans payable [Member] US term loan [Member] USD ($)	Jun. 30, 2012 Second Amended and Restated Credit Agreement [Member] Grand River Navigation Company, Inc. [Member] LIBOR [Member]	Jun. 30, 2012 Second Amended and Restated Credit Agreement [Member] Grand River Navigation Company, Inc. [Member] US Base Rate [Member]	Dec. 01, 2011 Second Amended and Restated Credit Agreement [Member] Grand River Navigation Company, Inc. [Member] Loans payable [Member] US term loan [Member] USD ($)	Jun. 30, 2012 Second Amended and Restated Credit Agreement [Member] Grand River Navigation Company, Inc. [Member] Loans payable [Member] US term loan [Member] USD ($)	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Grand River Navigation Company, Inc. [Member] Loans payable [Member] US term loan [Member] USD ($)	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Grand River Navigation Company, Inc. [Member] Loans payable [Member] US term loan [Member] LIBOR [Member]	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Grand River Navigation Company, Inc. [Member] Loans payable [Member] US term loan [Member] US Base Rate [Member]	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] USD ($)	Mar. 31, 2012 Second Amended and Restated Credit Agreement [Member] Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] LIBOR [Member]	Sep. 30, 2012 Second Amended and Restated Credit Agreement [Member] Black Creek Holdings, Inc. [Member] Loans payable [Member] Black Creek US term loan [Member] US Base Rate [Member]	Aug. 30, 2012 Secured Debt [Member] Third Amended & Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Canadian term loan [Member] CAD	Aug. 30, 2012 Secured Debt [Member] Third Amended & Restated Credit Agreement [Member] Grand River Navigation Company, Inc. [Member] US term loan [Member] USD ($)	Aug. 30, 2012 Secured Debt [Member] Third Amended & Restated Credit Agreement [Member] Black Creek Holdings, Inc. [Member] Black Creek US term loan [Member] USD ($)	Sep. 28, 2011 Secured Debt [Member] Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Canadian term loan [Member] CAD	Sep. 28, 2011 Secured Debt [Member] Second Amended and Restated Credit Agreement [Member] Lower Lakes Towing Ltd. [Member] Canadian engine loan [Member] USD ($)	Sep. 28, 2011 Secured Debt [Member] Second Amended and Restated Credit Agreement [Member] Grand River Navigation Company, Inc. [Member] US term loan [Member] USD ($)	Sep. 30, 2012 Component 1 [Member] Third Amended & Restated Credit Agreement [Member] CAD	Aug. 30, 2012 Component 1 [Member] Revolving Credit Facility [Member] Third Amended & Restated Credit Agreement [Member] CAD	Sep. 28, 2011 Component 1 [Member] Revolving Credit Facility [Member] Second Amended and Restated Credit Agreement [Member] CAD	Aug. 30, 2012 Component 1 [Member] Seasonal Overadvance Facility [Member] Third Amended & Restated Credit Agreement [Member] CAD	Sep. 28, 2011 Component 1 [Member] Seasonal Overadvance Facility [Member] Second Amended and Restated Credit Agreement [Member] CAD	Aug. 30, 2012 Component 1 [Member] Swing Line Facility [Member] Third Amended & Restated Credit Agreement [Member] CAD	Sep. 28, 2011 Component 1 [Member] Swing Line Facility [Member] Second Amended and Restated Credit Agreement [Member] CAD	Sep. 30, 2012 Component 2 [Member] Third Amended & Restated Credit Agreement [Member] USD ($)	Aug. 30, 2012 Component 2 [Member] Revolving Credit Facility [Member] Third Amended & Restated Credit Agreement [Member] USD ($)	Sep. 28, 2011 Component 2 [Member] Revolving Credit Facility [Member] Second Amended and Restated Credit Agreement [Member] USD ($)	Aug. 30, 2012 Component 2 [Member] Seasonal Overadvance Facility [Member] Third Amended & Restated Credit Agreement [Member] USD ($)	Dec. 01, 2011 Component 2 [Member] Seasonal Overadvance Facility [Member] Second Amended and Restated Credit Agreement [Member] USD ($)	Sep. 28, 2011 Component 2 [Member] Seasonal Overadvance Facility [Member] Second Amended and Restated Credit Agreement [Member] USD ($)	Aug. 30, 2012 Component 2 [Member] Swing Line Facility [Member] Third Amended & Restated Credit Agreement [Member] USD ($)	Sep. 28, 2011 Component 2 [Member] Swing Line Facility [Member] Second Amended and Restated Credit Agreement [Member] USD ($)
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity																																																																									13,500,000	13,500,000	13,500,000	12,000,000	10,000,000	4,000,000	4,000,000	$ 13,500,000	$ 13,500,000	$ 13,500,000	$ 12,000,000	$ 12,000,000	$ 10,000,000	$ 50,000	$ 4,000,000
Long-term Debt, Current and Noncurrent [Abstract]
Long-term debt	146,945,000		146,945,000		133,601,000																					53,884,000			0			64,127,000				28,934,000												55,386,000					6,015,000								42,233,000			29,967,000
Less amounts due within 12 months	3,674,000		3,674,000		9,686,000
Long-term debt, excluding current maturities	143,271,000		143,271,000		123,915,000
Basis spread on variable rate													4.75%					4.75%	3.75%	3.75%	4.75%	4.75%	3.75%				3.75%	4.75%					3.75%				4.75%	3.75%	3.50%	4.50%	3.50%	3.50%	4.50%	4.00%	5.00%				3.50%	4.50%				4.00%	5.00%		4.50%	3.50%				4.50%	3.50%		4.75%	3.75%
Debt Instrument, Increase, Additional Borrowings										25,000,000
Quarterly payment														(517,000)										(662,000)	(331,000)					802,000	(401,000)			(362,000)	(181,000)											(936,000)	(936,000)				(133,000)	(133,000)				(704,000)			(367,000)	(704,000)				(517,000)
Effective interest rate including effect of interest rate swap contracts						7.23%	6.91%	0.00%	6.28%		6.21%	6.22%
Effective interest rate						6.05%	5.78%	0.00%	6.28%		5.17%	4.98%			5.17%	5.31%
Debt Instrument, Face Amount																	31,000,000																																																		52,979,000	64,127,000	28,934,000	56,133,000	6,267,000	17,233,000
Gains (Losses) on Extinguishment of Debt	3,339,000	0	3,339,000	0
Payments of Debt Issuance Costs			$ 2,064,000