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Revenue Recognition Revenue Recognition (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2020
Disaggregation of Revenue [Line Items]          
Contract with Customer, Asset, after Allowance for Credit Loss $ 400.3   $ 400.3   $ 345.7
Contract with Customer, Liability 105.0   $ 105.0   $ 111.0
Percentage of Revenue, Remaining Performance Obligation     5.00%    
Out of Scope of Topic 606 Revenue [Member]          
Disaggregation of Revenue [Line Items]          
Fees and Commissions, Mortgage Banking and Servicing $ 102.3 $ 72.0 $ 235.9 $ 174.7