Derivatives (Schedule of Fair Value of Derivative Assets and Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value, Liability	$ (83,400)
Preferred Distribution Rate Reset Election | Other long-term liabilities
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value, Liability	(83,414)	$ (52,372)
Not qualifying or not designated as hedges under accounting rules | Commodity Derivatives | Current Assets - Other
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,693	732
Derivative Asset, Fair Value, Gross Liability	(1,693)	(732)
Asset Derivatives	0	0
Derivative Liability, Fair Value, Gross Liability	(3,315)	(2,114)
Derivative Liability, Fair Value, Gross Asset	3,315	2,114
Liability Derivatives	0	0
Not qualifying or not designated as hedges under accounting rules | Swaps | Current Assets - Other
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	616
Not qualifying or not designated as hedges under accounting rules | Swaps | Accrued Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(55)	0
Designated as hedges under accounting rules | Commodity Derivatives | Current Assets - Other
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	180	1,022
Derivative Asset, Fair Value, Gross Liability	(180)	(1,022)
Asset Derivatives	0	0
Derivative Liability, Fair Value, Gross Liability	(499)	(3,345)
Derivative Liability, Fair Value, Gross Asset	499	3,073
Liability Derivatives	$ 0	$ (272)