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Commitments and Contingencies (Restricted Cash and Marketable Securities) (Details) - USD ($)
$ in Millions
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]      
Financing proceeds $ 12.4 $ 0.0  
Capping, closure and post-closure obligations 42.4 31.5  
Insurance 84.2 117.6  
Total restricted cash and marketable securities $ 139.0 $ 149.1 $ 179.4