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Asset Retirement Obligations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Asset Retirement Obligation [Roll Forward]    
Beginning balance, ARO liability $ 19.8 $ 18.9
Additional ARO liability incurred 4.9 2.3
ARO liabilities settled (6.1) (2.2)
Accretion expense 2.1 1.3
Revisions in estimated cash flows 0.0 (0.5)
Ending balance, ARO liability $ 20.7 $ 19.8