Inventories (Schedule of Major Components of Inventories) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Petroleum products	$ 8,731,000	$ 11,550,000
Crude oil	29,873,000	73,133,000
Caustic soda	5,755,000	4,593,000
NaHS	8,277,000	9,304,000
Raw materials - Alkali Operations	4,550,000	0
Work-in-process - Alkali Operations	7,355,000	0
Finished goods, net - Alkali Operations	14,075,000	0
Materials and supplies, net - Alkali Operations	10,030,000	0
Other	7,000	7,000
Total	88,653,000	98,587,000
Inventory write-down	$ 0	$ 0