Fair-Value Measurements (Placement of Assets and Liabilities Within the Fair Value Hierarchy Levels) (Details) - Recurring Fair Value Measures - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Level 1 | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Fair Value	$ 7,544	$ 359
Liabilities Fair Value	(1,341)	(2,589)
Level 1 | Preferred Distribution Rate Reset Election
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities Fair Value	0	0
Level 2 | Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Fair Value	300	1,867
Liabilities Fair Value	(946)	(608)
Level 2 | Preferred Distribution Rate Reset Election
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities Fair Value	0	0
Level 3 | Commodity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Fair Value	0	0
Liabilities Fair Value	0	0
Level 3 | Preferred Distribution Rate Reset Election
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities Fair Value	$ (87,468)	$ (83,210)