Business Segment Information (Schedule of Revenues by Segment) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Total revenues	$ 1,630,415,000	$ 1,660,834,000	$ 1,721,323,000
Total Segment Margin	577,853,000	529,142,000	590,278,000
Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
Total revenues	531,898,000	404,919,000	382,154,000
Marine Transportation
Segment Reporting Information [Line Items]
Total revenues	319,498,000	321,616,000	327,464,000
Onshore Transportation and Services
Segment Reporting Information [Line Items]
Total revenues	779,019,000	934,299,000	1,011,705,000
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	1,630,415,000	1,660,834,000	1,721,323,000
Segment Operating Expenses	(601,852,000)	(582,935,000)	(615,349,000)
Segment Product Costs	(451,962,000)	(599,925,000)	(637,179,000)
Other Segment Items	1,252,000	51,168,000	121,483,000
Operating Segments | Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
Total revenues	531,035,000		377,842,000
Segment Operating Expenses	(145,005,000)	(117,207,000)	(96,025,000)
Segment Product Costs	0	0	0
Other Segment Items	(1,199,000)	45,074,000	120,543,000
Total Segment Margin	385,694,000	332,786,000	406,672,000
Operating Segments | Marine Transportation
Segment Reporting Information [Line Items]
Total revenues	319,498,000		327,464,000
Segment Operating Expenses	(204,830,000)	(196,602,000)	(218,403,000)
Segment Product Costs	0	0	0
Other Segment Items	1,022,000	(11,000)	1,362,000
Total Segment Margin	115,690,000	125,003,000	110,423,000
Operating Segments | Onshore Transportation and Services
Segment Reporting Information [Line Items]
Total revenues	779,882,000		1,016,017,000
Segment Operating Expenses	(252,017,000)	(269,126,000)	(300,921,000)
Segment Product Costs	(451,962,000)	(599,925,000)	(637,179,000)
Other Segment Items	1,429,000	6,105,000	(422,000)
Total Segment Margin	76,469,000	$ 71,353,000	73,183,000
Intersegment
Segment Reporting Information [Line Items]
Total revenues	0		0
Intersegment | Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
Total revenues	863,000		4,312,000
Intersegment | Marine Transportation
Segment Reporting Information [Line Items]
Total revenues	0		0
Intersegment | Onshore Transportation and Services
Segment Reporting Information [Line Items]
Total revenues	$ (863,000)		$ (4,312,000)