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Asset Retirement Obligations (ARO) (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2023
Sep. 30, 2022
Dec. 31, 2022
Asset Retirement Obligation Roll Forward          
Balance at beginning of period     $ 43.3 $ 39.2 $ 39.2
Accretion expense $ 0.7 $ 0.6 2.2 $ 2.0 2.7
Settlements of liabilities     (3.1)   (2.3)
Liabilities incurred     1.6   3.7
Balance at end of period $ 44.0   $ 44.0   $ 43.3