Derivatives (Schedule of Effect on Operating Results) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Commodity Derivatives | Onshore Facilities and Transportation Product Costs & Sodium Minerals and Sulfur Services Operating costs [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income	$ (1,698)	$ 7,379
Commodity Derivatives | Designated as Hedging Instrument | Onshore facilities and transportation product costs
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income	(1,366)	6,286
Commodity Derivatives | Not Designated As Hedging Instrument | Onshore Facilities and Transportation Product Costs & Sodium Minerals and Sulfur Services Operating costs [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income	(332)	1,093
Swap | Not Designated As Hedging Instrument | Sodium minerals and sulfur services operating costs
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income	(275)	0
Preferred Distribution Rate Reset Election | Other expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income	$ (1,906)	$ 0