SEGMENT DATA (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) Segment	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
SEGMENT DATA [Abstract]
Number of reportable segments | Segment			2
Revenues [Abstract]
Marine transportation	$ 318,810	$ 359,031	$ 993,727	$ 1,115,677
Distribution and services	222,464	75,677	512,580	219,346
Total revenues	541,274	434,708	1,506,307	1,335,023
Segment profit (loss)	47,861	51,559	131,874	175,376
Total assets	5,200,415		5,200,415		$ 4,289,895
Other segment disclosures [Abstract]
Gain (loss) on disposition of assets	(159)	(122)	(199)	39
Interest expense	(5,388)	(4,507)	(14,310)	(13,213)
Other income (expense)	(113)	(120)	(230)	194
Corporate and Other [Member]
Revenues [Abstract]
Segment profit (loss)	(10,155)	(8,535)	(27,251)	(24,465)
Total assets	50,943		50,943		52,676
Other segment disclosures [Abstract]
Loss from other segment	(10,155)	(8,535)	(27,251)	(24,465)
Details of "Other" total assets [Abstract]
Total other assets	50,943		50,943		52,676
Reporting Segments [Member]
Revenues [Abstract]
Marine transportation	318,810	359,031	993,727	1,115,677
Distribution and services	222,464	75,677	512,580	219,346
Reporting Segments [Member] | Marine Transportation [Member]
Revenues [Abstract]
Segment profit (loss)	36,042	55,460	107,062	197,981
Total assets	3,589,535		3,589,535		3,613,951
Reporting Segments [Member] | Distribution and Services [Member]
Revenues [Abstract]
Segment profit (loss)	21,974	4,634	52,063	1,860
Total assets	1,559,937		1,559,937		623,268
Intersegment Eliminations [Member] | Marine Transportation [Member]
Revenues [Abstract]
Total revenues	4,967	7,171	15,342	17,722
Segment profit (loss)	497	717	1,534	1,772
Other [Member]
Other segment disclosures [Abstract]
General corporate expenses	(4,495)	(3,786)	(12,512)	(11,485)
Gain (loss) on disposition of assets	(159)	(122)	(199)	39
Interest expense	(5,388)	(4,507)	(14,310)	(13,213)
Other income (expense)	(113)	$ (120)	(230)	$ 194
Details of "Other" total assets [Abstract]
General corporate assets	49,092		49,092		50,054
Investment in affiliates	$ 1,851		$ 1,851		$ 2,622