Business Segment Information (Schedule of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Segment margin	$ 152,136	$ 139,325	$ 308,233	$ 308,613
Total revenues	503,855	388,467	1,025,074	928,390
Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
Total revenues	73,221	64,964	137,605	143,393
Sodium Minerals & Sulfur Services
Segment Reporting Information [Line Items]
Total revenues	237,087	192,624	464,374	436,014
Onshore Facilities and Transportation
Segment Reporting Information [Line Items]
Total revenues	145,921	74,159	335,138	229,917
Marine Transportation
Segment Reporting Information [Line Items]
Total revenues	47,626	56,720	87,957	119,066
Operating Segments
Segment Reporting Information [Line Items]
Segment margin	152,136	139,325	308,233	308,613
Capital expenditures	113,625	39,767	148,004	71,158
Total revenues	503,855	388,467	1,025,074	928,390
Operating Segments | Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
Segment margin	83,106	75,148	167,375	160,394
Capital expenditures	19,421	1,983	30,949	3,010
Total revenues	73,221	64,964	137,605	143,393
Operating Segments | Sodium Minerals & Sulfur Services
Segment Reporting Information [Line Items]
Segment margin	38,194	24,824	81,914	61,765
Capital expenditures	80,560	33,462	90,598	48,437
Total revenues	239,258	194,543	468,564	440,078
Operating Segments | Onshore Facilities and Transportation
Segment Reporting Information [Line Items]
Segment margin	22,368	21,215	43,367	49,314
Capital expenditures	2,487	829	3,586	1,986
Total revenues	144,406	74,690	332,556	231,489
Operating Segments | Marine Transportation
Segment Reporting Information [Line Items]
Segment margin	8,468	18,138	15,577	37,140
Capital expenditures	11,157	3,493	22,871	17,725
Total revenues	46,970	54,270	86,349	113,430
Intersegment
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Intersegment | Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Intersegment | Sodium Minerals & Sulfur Services
Segment Reporting Information [Line Items]
Total revenues	(2,171)	(1,919)	(4,190)	(4,064)
Intersegment | Onshore Facilities and Transportation
Segment Reporting Information [Line Items]
Total revenues	1,515	(531)	2,582	(1,572)
Intersegment | Marine Transportation
Segment Reporting Information [Line Items]
Total revenues	$ 656	$ 2,450	$ 1,608	$ 5,636