Business Segment Information (Schedule of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Segment margin	$ 175,819	$ 183,207	$ 533,495	$ 527,301
Total revenues	621,697	745,278	1,876,491	2,223,474
Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
Total revenues	79,738	70,115	236,482	213,344
Sodium Minerals & Sulfur Services
Segment Reporting Information [Line Items]
Total revenues	277,527	291,722	827,619	876,513
Onshore Facilities & Transportation
Segment Reporting Information [Line Items]
Total revenues	205,028	327,145	637,630	972,207
Marine Transportation
Segment Reporting Information [Line Items]
Total revenues	59,404	56,296	174,760	161,410
Operating Segments
Segment Reporting Information [Line Items]
Segment margin	175,819	183,207	533,495	527,301
Capital expenditures	42,751	43,019	115,281	129,917
Total revenues	621,697	745,278	1,876,491	2,223,474
Operating Segments | Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
Segment margin	81,060	70,963	233,978	215,738
Capital expenditures	1,996	564	4,975	2,665
Total revenues	79,738	70,115	236,482	213,344
Operating Segments | Sodium Minerals & Sulfur Services
Segment Reporting Information [Line Items]
Segment margin	55,258	63,942	171,602	192,875
Capital expenditures	26,415	20,819	75,258	49,078
Total revenues	279,416	293,491	833,278	881,822
Operating Segments | Onshore Facilities & Transportation
Segment Reporting Information [Line Items]
Segment margin	24,829	36,189	86,352	83,622
Capital expenditures	1,599	16,700	5,383	52,559
Total revenues	205,913	327,844	640,716	976,193
Operating Segments | Marine Transportation
Segment Reporting Information [Line Items]
Segment margin	14,672	12,113	41,563	35,066
Capital expenditures	12,741	4,936	29,665	25,615
Total revenues	56,630	53,828	166,015	152,115
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	(1,889)	(1,769)	(5,659)	(5,309)
Intersegment | Onshore Facilities & Transportation
Segment Reporting Information [Line Items]
Total revenues	(885)	(699)	(3,086)	(3,986)
Intersegment | Marine Transportation
Segment Reporting Information [Line Items]
Total revenues	$ 2,774	$ 2,468	$ 8,745	$ 9,295