Segment Data (Details)	3 Months Ended
	Mar. 31, 2020 USD ($) Segment	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Segment Data [Abstract]
Number of reportable segments | Segment	2
Revenues [Abstract]
Revenues	$ 643,926,000	$ 744,621,000
Segment profit (loss)	(519,772,000)	58,337,000
Total assets	6,009,644,000		$ 6,079,097,000
Other segment disclosures [Abstract]
Interest expense	(12,799,000)	(13,201,000)
Gain on disposition of assets	492,000	2,157,000
Other income (expense)	2,723,000	(568,000)
Earnings (loss) before taxes on income	(519,772,000)	58,337,000
Marine Transportation [Member]
Revenues [Abstract]
Revenues	403,257,000	368,121,000
Distribution and Services [Member]
Revenues [Abstract]
Revenues	240,669,000	376,500,000
Other [Member]
Revenues [Abstract]
Segment profit (loss)	(574,206,000)	(14,696,000)
Total assets	556,164,000		120,335,000
Other segment disclosures [Abstract]
General corporate expenses	(3,348,000)	(3,084,000)
Interest expense	(12,799,000)	(13,201,000)
Impairments and other charges	(561,274,000)	0
Gain on disposition of assets	492,000	2,157,000
Other income (expense)	2,723,000	(568,000)
Earnings (loss) before taxes on income	(574,206,000)	(14,696,000)
Details of "Other" total assets [Abstract]
General corporate assets	553,965,000		118,310,000
Investment in affiliates	2,199,000		2,025,000
Total other assets	556,164,000		120,335,000
Reporting Segments [Member] | Marine Transportation [Member]
Revenues [Abstract]
Revenues	403,257,000	368,121,000
Segment profit (loss)	50,716,000	35,424,000
Total assets	4,565,489,000		4,536,368,000
Other segment disclosures [Abstract]
Earnings (loss) before taxes on income	50,716,000	35,424,000
Reporting Segments [Member] | Distribution and Services [Member]
Revenues [Abstract]
Revenues	240,669,000	376,500,000
Segment profit (loss)	3,718,000	37,609,000
Total assets	887,991,000		$ 1,422,394,000
Other segment disclosures [Abstract]
Earnings (loss) before taxes on income	3,718,000	37,609,000
Intersegment Eliminations [Member]
Revenues [Abstract]
Revenues	10,286,000	7,535,000
Segment profit (loss)	1,029,000	754,000
Other segment disclosures [Abstract]
Earnings (loss) before taxes on income	$ 1,029,000	$ 754,000