SEGMENT DATA (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) Segment	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
SEGMENT DATA [Abstract]
Number of reportable segments | Segment			2
Revenues [Abstract]
Revenues	$ 771,042,000	$ 802,671,000	$ 1,515,663,000	$ 1,544,359,000
Segment profit (loss)	62,709,000	44,854,000	121,046,000	87,385,000
Total assets	6,232,890,000		6,232,890,000		$ 5,871,594,000
Other segment disclosures [Abstract]
Gain on disposition of assets	3,118,000	442,000	5,275,000	2,340,000
Interest expense	(15,515,000)	(12,540,000)	(28,716,000)	(22,320,000)
Other income	2,381,000	1,541,000	1,813,000	3,132,000
Earnings before taxes on income	62,709,000	44,854,000	121,046,000	87,385,000
Marine Transportation [Member]
Revenues [Abstract]
Revenues	404,286,000	378,163,000	772,407,000	718,566,000
Distribution and Services [Member]
Revenues [Abstract]
Revenues	366,756,000	424,508,000	743,256,000	825,793,000
Other [Member]
Revenues [Abstract]
Segment profit (loss)	(13,662,000)	(33,564,000)	(28,358,000)	(44,178,000)
Total assets	110,574,000		110,574,000		72,664,000
Other segment disclosures [Abstract]
General corporate expenses	(3,646,000)	(23,007,000)	(6,730,000)	(27,330,000)
Gain on disposition of assets	3,118,000	442,000	5,275,000	2,340,000
Interest expense	(15,515,000)	(12,540,000)	(28,716,000)	(22,320,000)
Other income	2,381,000	1,541,000	1,813,000	3,132,000
Earnings before taxes on income	(13,662,000)	(33,564,000)	(28,358,000)	(44,178,000)
Details of "Other" total assets [Abstract]
General corporate assets	108,786,000		108,786,000		70,169,000
Investment in affiliates	1,788,000		1,788,000		2,495,000
Total other assets	110,574,000		110,574,000		72,664,000
Reporting Segments [Member] | Marine Transportation [Member]
Revenues [Abstract]
Revenues	404,286,000	378,163,000	772,407,000	718,566,000
Segment profit (loss)	53,243,000	38,228,000	88,667,000	54,408,000
Total assets	4,550,455,000		4,550,455,000		4,145,294,000
Other segment disclosures [Abstract]
Earnings before taxes on income	53,243,000	38,228,000	88,667,000	54,408,000
Reporting Segments [Member] | Distribution and Services [Member]
Revenues [Abstract]
Revenues	366,756,000	424,508,000	743,256,000	825,793,000
Segment profit (loss)	23,128,000	40,190,000	60,737,000	77,155,000
Total assets	1,571,861,000		1,571,861,000		$ 1,653,636,000
Other segment disclosures [Abstract]
Earnings before taxes on income	23,128,000	40,190,000	60,737,000	77,155,000
Intersegment Eliminations [Member]
Revenues [Abstract]
Revenues	7,446,000	7,770,000	14,981,000	15,920,000
Segment profit (loss)	744,000	777,000	1,498,000	1,592,000
Other segment disclosures [Abstract]
Earnings before taxes on income	$ 744,000	$ 777,000	$ 1,498,000	$ 1,592,000