Business Segment Information (Schedule of Total Assets By Reportable Segment) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
TOTAL ASSETS	$ 7,137,481	$ 5,702,592	$ 5,459,599
Other assets
Segment Reporting Information [Line Items]
TOTAL ASSETS	49,737	43,089	48,208
Offshore Pipeline Transportation
Segment Reporting Information [Line Items]
TOTAL ASSETS	2,486,803	2,575,335	2,623,478
Sodium Minerals and Sulfur Services
Segment Reporting Information [Line Items]
TOTAL ASSETS	1,848,188	395,043	394,626
Onshore Facilities and Transportation
Segment Reporting Information [Line Items]
TOTAL ASSETS	1,927,976	1,875,403	1,615,335
Marine Transportation
Segment Reporting Information [Line Items]
TOTAL ASSETS	$ 824,777	$ 813,722	$ 777,952