ACQUISITIONS (Details)		9 Months Ended
	Mar. 14, 2019 USD ($) bbl Towboat Tugboat TankBarge	Sep. 30, 2019 USD ($) TankBarge	Sep. 30, 2018 USD ($)
Acquisitions [Abstract]
Purchase price		$ 184,068,000	$ 231,752,000
Inland Tank Barges [Member]
Acquisitions [Abstract]
Number of maritime vessels acquired | TankBarge		9
Purchase price		$ 13,040,000
Average age of property		5 years
Cenac Marine Services, LLC [Member]
Assets [Abstract]
Prepaid expenses	$ 1,138,000
Property and equipment	247,122,000
Other intangibles	340,000
Total assets	248,600,000
Other long-term liabilities	4,100,000
Net assets acquired	$ 244,500,000
Weighted average amortization period of intangibles		2 years
Weighted average amortization period of unfavorable contracts		1 year 3 months 18 days
Acquisition related costs		$ 442,000
Cenac Marine Services, LLC [Member] | Inland Barrel Tank Barges [Member]
Acquisitions [Abstract]
Number of maritime vessels acquired | TankBarge	63
Tank barge barrel capacity (in barrels) | bbl	30,000
Aggregate tank barge barrel capacity (in barrels) | bbl	1,833,000
Cenac Marine Services, LLC [Member] | Inland Towboats [Member]
Acquisitions [Abstract]
Number of maritime vessels acquired | Towboat	34
Average age of property		7 years
Cenac Marine Services, LLC [Member] | Offshore Tugboats [Member]
Acquisitions [Abstract]
Number of maritime vessels acquired | Tugboat	2