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Receivables And Concentration Of Credit Risk (Narrative) (Details)
$ in Millions
3 Months Ended 6 Months Ended
Mar. 31, 2019
USD ($)
customer
Mar. 31, 2018
Mar. 31, 2019
USD ($)
customer
Mar. 31, 2018
Sep. 30, 2018
USD ($)
customer
Receivables [Line Items]          
Allowance for uncollectible receivables | $ $ 4.3   $ 4.3   $ 4.2
Major Customer Three [Member] | Sales Revenue Net And/Or Trade Accounts Receivable [Member]          
Receivables [Line Items]          
Number of major customers accounting for a significant percentage of sales and/or receivables volume | customer 3   3   3
Major Customer Three [Member] | Sales Revenue Net And/Or Trade Accounts Receivable [Member] | Minimum [Member]          
Receivables [Line Items]          
Concentration risk 10.00%   10.00%   10.00%
Major Customer Three [Member] | Net Sales [Member]          
Receivables [Line Items]          
Concentration risk 42.20% 36.10% 35.90% 33.10%  
Major Customer Three [Member] | Trade Receivable [Member]          
Receivables [Line Items]          
Concentration risk 33.90%   33.90%   37.20%