Segment Data (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) Segment	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment			2
Revenues [Abstract]
Total revenues	$ 697,964,000	$ 559,624,000	$ 1,308,746,000	$ 1,056,474,000
Segment profit (loss)	39,636,000	15,845,000	63,435,000	11,834,000
Total assets	5,405,156,000		5,405,156,000		$ 5,399,063,000
Other segment disclosures [Abstract]
Gain on disposition of assets	2,745,000	2,119,000	7,594,000	4,252,000
Interest expense	(10,640,000)	(10,706,000)	(20,843,000)	(21,672,000)
Earnings before taxes on income	39,636,000	15,845,000	63,435,000	11,834,000
Marine Transportation [Member]
Revenues [Abstract]
Total revenues	405,655,000	332,887,000	761,191,000	633,838,000
Distribution and Services [Member]
Revenues [Abstract]
Total revenues	292,309,000	226,737,000	547,555,000	422,636,000
Other [Member]
Revenues [Abstract]
Segment profit (loss)	(7,918,000)	(8,789,000)	(12,025,000)	(17,651,000)
Total assets	173,724,000		173,724,000		187,380,000
Other segment disclosures [Abstract]
General corporate expenses	(3,763,000)	(2,725,000)	(6,824,000)	(6,545,000)
Gain on disposition of assets	2,745,000	2,119,000	7,594,000	4,252,000
Interest expense	(10,640,000)	(10,706,000)	(20,843,000)	(21,672,000)
Other income	3,740,000	2,523,000	8,048,000	6,314,000
Earnings before taxes on income	(7,918,000)	(8,789,000)	(12,025,000)	(17,651,000)
Details of Other total assets [Abstract]
General corporate assets	171,996,000		171,996,000		185,246,000
Investment in affiliates	1,728,000		1,728,000		2,134,000
Total other assets	173,724,000		173,724,000		187,380,000
Reporting Segments [Member] | Marine Transportation [Member]
Revenues [Abstract]
Total revenues	405,655,000	332,887,000	761,191,000	633,838,000
Segment profit (loss)	30,817,000	18,478,000	47,752,000	20,418,000
Total assets	4,304,291,000		4,304,291,000		4,319,080,000
Other segment disclosures [Abstract]
Earnings before taxes on income	30,817,000	18,478,000	47,752,000	20,418,000
Reporting Segments [Member] | Distribution and Services [Member]
Revenues [Abstract]
Total revenues	292,309,000	226,737,000	547,555,000	422,636,000
Segment profit (loss)	16,737,000	6,156,000	27,708,000	9,067,000
Total assets	927,141,000		927,141,000		$ 892,603,000
Other segment disclosures [Abstract]
Earnings before taxes on income	16,737,000	6,156,000	27,708,000	9,067,000
Intersegment Eliminations [Member]
Revenues [Abstract]
Total revenues	6,300,000	7,300,000	13,900,000	12,200,000
Segment profit (loss)	600,000	700,000	1,400,000	1,200,000
Other segment disclosures [Abstract]
Earnings before taxes on income	$ 600,000	$ 700,000	$ 1,400,000	$ 1,200,000