Derivatives (Schedule of Fair Value of Derivative Assets and Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value, Liability	$ (85,200)
Preferred Distribution Rate Reset Election | Other long-term liabilities
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value, Liability	(85,154)	$ (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	65	732
Derivative Asset, Fair Value, Gross Liability	(65)	(732)
Asset Derivatives	0	0
Derivative Liability, Fair Value, Gross Liability	(605)	(2,114)
Derivative Liability, Fair Value, Gross Asset	605	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
Designated as hedges under accounting rules | Commodity Derivatives | Current Assets - Other
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	13	1,022
Derivative Asset, Fair Value, Gross Liability	(13)	(1,022)
Asset Derivatives	0	0
Derivative Liability, Fair Value, Gross Liability	(267)	(3,345)
Derivative Liability, Fair Value, Gross Asset	267	3,073
Liability Derivatives	$ 0	$ (272)