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Income Taxes (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Mar. 31, 2021
Mar. 31, 2020
Sep. 30, 2020
Sep. 30, 2018
Income Taxes [Line Items]            
Effective Tax Rate 26.30% (53.20%) 26.80% 139.90%    
Valuation Allowance $ 63.9 $ 56.8 $ 63.9 $ 56.8    
First Installment of AMT Credit Refunds Received         $ 42.5  
Accelerated AMT Credit Refund Received Under CARES Act         $ 42.5  
Alternative Minimum Tax Credit [Member]            
Income Taxes [Line Items]            
Tax Credit Carryforwards           $ 85.0