SEGMENT DATA (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) Segment	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
SEGMENT DATA [Abstract]
Number of reportable segments | Segment	2
Revenues [Abstract]
Revenues	$ 741,688	$ 491,705
Segment profit (loss)	42,531	40,998
Total assets	5,714,500		$ 5,127,427
Other segment disclosures [Abstract]
Gain on disposition of assets	1,898	99
Interest expense	(9,780)	(4,457)
Other income (expense)	1,591	(589)
Marine Transportation [Member]
Revenues [Abstract]
Revenues	340,403	343,652
Distribution and Services [Member]
Revenues [Abstract]
Revenues	401,285	148,053
Other [Member]
Revenues [Abstract]
Segment profit (loss)	(10,614)	(8,475)
Total assets	60,560		75,243
Other segment disclosures [Abstract]
General corporate expenses	(4,323)	(3,528)
Gain on disposition of assets	1,898	99
Interest expense	(9,780)	(4,457)
Other income (expense)	1,591	(589)
Loss from other segment	(10,614)	(8,475)
Details of "Other" total assets [Abstract]
General corporate assets	58,535		73,353
Investment in affiliates	2,025		1,890
Total other assets	60,560		75,243
Reporting Segments [Member] | Marine Transportation [Member]
Revenues [Abstract]
Revenues	340,403	343,652
Segment profit (loss)	16,180	35,768
Total assets	4,022,420		3,485,099
Reporting Segments [Member] | Distribution and Services [Member]
Revenues [Abstract]
Revenues	401,285	148,053
Segment profit (loss)	36,965	13,705
Total assets	1,631,520		$ 1,567,085
Intersegment Eliminations [Member]
Revenues [Abstract]
Revenues	8,150	5,430
Segment profit (loss)	$ 815	$ 543