Derivatives (Schedule of Effect on Operating Results) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Commodity derivatives - futures and call options | Cost of Goods and Services Sold
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income	$ 321	$ 1,600	$ (13,903)	$ (7,210)
Natural Gas Swap Liability | Cost of Goods and Services Sold | Sodium minerals and sulfur services operating costs
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income	666	81	1,217	1,316
Preferred Distribution Rate Reset Election | Other income, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income	6,689	7,974	17,395	306
Contracts designated as hedges under accounting guidance | Commodity derivatives - futures and call options | Cost of Goods and Services Sold | Onshore facilities and transportation product costs
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income	(854)	227	(11,061)	(492)
Contracts not considered hedges under accounting guidance | Commodity derivatives - futures and call options | Cost of Goods and Services Sold | Onshore facilities and transportation product costs, sodium minerals and sulfur services operating costs
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income	$ 1,175	$ 1,373	$ (2,842)	$ (6,718)