Business Segment Information (Schedule of Total Assets by Reportable Segment) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total consolidated assets	$ 7,137,634	$ 5,702,592
Offshore pipeline transportation
Segment Reporting Information [Line Items]
Total consolidated assets	2,507,540	2,575,335
Sodium minerals and sulfur services
Segment Reporting Information [Line Items]
Total consolidated assets	1,826,815	395,043
Marine transportation
Segment Reporting Information [Line Items]
Total consolidated assets	811,870	813,722
Onshore Facilities & Transportation
Segment Reporting Information [Line Items]
Total consolidated assets	1,939,355	1,875,403
Other assets
Segment Reporting Information [Line Items]
Total consolidated assets	$ 52,054	$ 43,089