Business Segment Information (Schedule of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Segment margin	$ 173,854	$ 134,000	$ 344,094	$ 272,645
Total revenues	752,388	406,723	1,478,196	822,214
Offshore pipeline transportation
Segment Reporting Information [Line Items]
Total revenues	69,969	77,638	143,229	162,766
Sodium minerals and sulfur services
Segment Reporting Information [Line Items]
Total revenues	298,881	43,068	584,791	88,114
Onshore Facilities & Transportation
Segment Reporting Information [Line Items]
Total revenues	327,353	232,815	645,062	467,830
Marine transportation
Segment Reporting Information [Line Items]
Total revenues	56,185	53,202	105,114	103,504
Operating Segments
Segment Reporting Information [Line Items]
Segment margin	173,854	134,000	344,094	272,645
Capital Expenditures	42,391	57,850	86,898	116,837
External customers	752,388	406,723	1,478,196	822,214
Operating Segments | Offshore pipeline transportation
Segment Reporting Information [Line Items]
Segment margin	71,602	78,211	144,775	165,300
Capital Expenditures	1,447	3,903	2,101	6,142
External customers	69,969	78,577	143,229	163,982
Operating Segments | Sodium minerals and sulfur services
Segment Reporting Information [Line Items]
Segment margin	64,542	16,337	128,933	33,833
Capital Expenditures	18,560	432	28,259	945
External customers	300,928	45,210	588,331	92,481
Operating Segments | Onshore Facilities & Transportation
Segment Reporting Information [Line Items]
Segment margin	25,744	25,296	47,433	46,393
Capital Expenditures	12,570	42,383	35,859	89,085
External customers	328,134	233,625	648,349	468,236
Operating Segments | Marine transportation
Segment Reporting Information [Line Items]
Segment margin	11,966	14,156	22,953	27,119
Capital Expenditures	9,814	11,132	20,679	20,665
External customers	53,357	49,311	98,287	97,515
Intersegment
Segment Reporting Information [Line Items]
Intersegment	0	0	0	0
Intersegment | Offshore pipeline transportation
Segment Reporting Information [Line Items]
Intersegment	0	(939)	0	(1,216)
Intersegment | Sodium minerals and sulfur services
Segment Reporting Information [Line Items]
Intersegment	(2,047)	(2,142)	(3,540)	(4,367)
Intersegment | Onshore Facilities & Transportation
Segment Reporting Information [Line Items]
Intersegment	(781)	(810)	(3,287)	(406)
Intersegment | Marine transportation
Segment Reporting Information [Line Items]
Intersegment	$ 2,828	$ 3,891	$ 6,827	$ 5,989