Fixed Assets and Mineral Leaseholds (Schedule of Fixed Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fixed assets, at cost	$ 5,686,153	$ 5,601,015
Less: Accumulated depreciation	(867,465)	(734,986)
Net fixed assets	4,818,688	4,866,029
Crude oil pipelines and natural gas pipelines and related assets
Fixed assets, at cost	3,090,475	3,028,657
Onshore facilities, machinery, and equipment
Fixed assets, at cost	725,624	692,364
Onshore facilities, machinery, and equipment \| Alkali Business
Fixed assets, at cost	506,924	497,601
Transportation equipment
Fixed assets, at cost	21,529	21,483
Marine vessels
Fixed assets, at cost	935,823	918,953
Land, buildings and improvements
Fixed assets, at cost	230,665	223,186
Office equipment, furniture and fixtures
Fixed assets, at cost	18,924	18,112
Construction in progress
Fixed assets, at cost	104,592	151,768
Other
Fixed assets, at cost	$ 51,597	$ 48,891

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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