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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 Analysis [Roll Forward]    
Net asset retirement obligations at January 1 $ 35.1 $ 34.8
Liabilities acquired 0.0 0.3
Liabilities incurred 0.0 0.3
Liabilities settled (0.4) (0.8)
Accretion expense (1.9) (1.9)
Other (0.4) (1.4)
Net asset retirement obligation at December 31 36.2 35.1
Asset retirement obligations $ 1.4 $ 1.0