Financial Instruments and Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes receivable from municipalities, Carrying Cost	$ 13,382	$ 13,462
Investments in short-term time deposits, Carrying Cost	12,123	8,874
Long-term debt, Carrying Cost	(1,013,737)	(1,095,292)
Fair Value Hierarchy Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes receivable from municipalities, Estimated Fair Value	14,037	13,458
Investments in short-term time deposits, Estimated Fair Value	12,072	8,883
Long-term debt, Estimated Fair Value	$ (1,065,531)	$ (1,094,987)