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Business and Summary of Significant Accounting Policies - Basis of Presentation (Details) - USD ($)
$ / shares in Units, $ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Business And Organization [Line Items]      
Net income (loss) $ 286.5 $ 174.0 $ 157.8
Decrease in diluted earnings (loss) per common share (in dollars per share) $ (15.51) $ (9.34) $ (7.83)
Restatement Adjustment      
Business And Organization [Line Items]      
Out-of-period adjustment $ 10.6    
Net income (loss) $ (9.7)    
Decrease in diluted earnings (loss) per common share (in dollars per share) $ 0.53