Financial Instruments and Fair Value Measurements (Narrative) (Details) $ in Thousands	Sep. 30, 2019 USD ($) item	Sep. 30, 2018 USD ($) item
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial assets on recurring basis	$ 144,335	$ 103,324
Financial liability on recurring basis		23,000
Other Assets [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial assets on recurring basis	$ 24,758
Other Liabilities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Financial liability on recurring basis		$ 23,000
Investments in Short-Term Time Deposits [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate used to measure short-term time deposits | item	5.7	6.3
Long Term Notes Receivable From Municipalities [Member] | Measurement Input, Discount Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate used to measure municipal notes | item	1.7	3.1
Long-Term Debt [Member] | Measurement Input, Discount Rate [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Interest rate used to measure long-term debt | item	2.5	3.5
Cash [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	$ 52,971	$ 59,838
Investments in Reverse Repurchase Agreements [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	886	4,582
Investments in Term Deposits with Foreign Banks [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	$ 45,216	19,174
Restricted Investments in Term Deposits with Foreign Banks [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		$ 3,635