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Asset Retirement Obligations - Roll-Forward (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Change in asset retirement obligations    
Asset retirement obligations at the beginning of year $ 797,762 $ 767,382
Changes attributable to:    
Accretion expense 44,269 41,240
Settlements (14,039) (10,860)
Estimated cash flow revisions 135,323 0
Newly incurred obligation 2,686 0
Asset retirement obligations at the end of year $ 966,001 $ 797,762