Business Segment Information (Schedule of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Segment margin	$ 153,862	$ 161,857	$ 462,095	$ 470,470
Total revenues	518,821	443,125	1,543,895	1,371,515
Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
Total revenues	69,479	53,893	207,084	197,286
Sodium Minerals & Sulfur Services
Segment Reporting Information [Line Items]
Total revenues	237,651	206,731	702,025	642,745
Onshore Facilities and Transportation
Segment Reporting Information [Line Items]
Total revenues	162,975	130,589	498,113	360,506
Marine Transportation
Segment Reporting Information [Line Items]
Total revenues	48,716	51,912	136,673	170,978
Operating Segments
Segment Reporting Information [Line Items]
Segment margin	153,862	161,857	462,095	470,470
Capital expenditures	79,217	28,843	227,221	100,001
Total revenues	518,821	443,125	1,543,895	1,371,515
Operating Segments | Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
Segment margin	76,045	57,380	243,420	217,774
Capital expenditures	3,819	2,899	34,768	5,909
Total revenues	69,479	53,870	207,084	197,263
Operating Segments | Sodium Minerals & Sulfur Services
Segment Reporting Information [Line Items]
Segment margin	39,649	27,592	121,563	89,357
Capital expenditures	67,583	19,225	158,181	67,662
Total revenues	240,048	208,909	708,612	648,987
Operating Segments | Onshore Facilities and Transportation
Segment Reporting Information [Line Items]
Segment margin	29,145	61,298	72,512	110,612
Capital expenditures	929	1,446	4,515	3,432
Total revenues	161,296	130,440	493,852	361,929
Operating Segments | Marine Transportation
Segment Reporting Information [Line Items]
Segment margin	9,023	15,587	24,600	52,727
Capital expenditures	6,886	5,273	29,757	22,998
Total revenues	47,998	49,906	134,347	163,336
Intersegment
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Intersegment | Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
Total revenues	0	23	0	23
Intersegment | Sodium Minerals & Sulfur Services
Segment Reporting Information [Line Items]
Total revenues	(2,397)	(2,178)	(6,587)	(6,242)
Intersegment | Onshore Facilities and Transportation
Segment Reporting Information [Line Items]
Total revenues	1,679	149	4,261	(1,423)
Intersegment | Marine Transportation
Segment Reporting Information [Line Items]
Total revenues	$ 718	$ 2,006	$ 2,326	$ 7,642