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Long-Term Debt - Revolving Credit Facility (Details) - Revolving Credit Facility
Nov. 09, 2020
USD ($)
Mar. 31, 2021
USD ($)
Sep. 30, 2020
USD ($)
Line of Credit Facility [Line Items]      
Borrowings outstanding   $ 0 $ 0
Letters of credit outstanding   0 $ 0
Amended Revolving Credit Facility      
Line of Credit Facility [Line Items]      
Revolving credit facility increased $ 60,000,000    
Maximum borrowing capacity $ 685,000,000    
Priority-debt-to-EBITDA ratio 2.25    
Current borrowing capacity   276,000,000  
Maximum limit on issuance, letters of credit   $ 100,000,000