Financial Instruments and Fair Value Measurements (Narrative) (Details) - Measurement Input, Discount Rate [Member]	Mar. 31, 2021	Sep. 30, 2020
Long-Term Debt [Member] | Weighted Average [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Interest rate used to measure long-term debt	1.7	1.5
Long Term Notes Receivable from Municipalities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Interest rate used to measure municipal notes	1.3	1.2
Interest rate used to measure promissory notes	2.0	2.3
Investments in Short-Term Time Deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Interest rate used to measure short-term time deposits	4.4	4.4