Financial Instruments and Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details) - Level 2 [Member] - USD ($) $ in Thousands	Dec. 31, 2024	Sep. 30, 2024
ASSETS
Investments in short-term time deposits, Estimated Fair Value	$ 2,999	$ 3,064
Liabilities:
Long-term debt, Estimated Fair Value	617,151	634,071
Investments in short-term time deposits, Carrying Cost	2,997	3,064
Long-term debt, Carrying Cost	644,980	656,360
Long Term Notes Receivable from Municipalities [Member]
ASSETS
Notes receivable, Estimated Fair Value	6,491	6,961
Liabilities:
Notes receivable, Carrying Cost	$ 6,143	$ 6,514