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Financial Instruments and Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended
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Jun. 30, 2018 | Sep. 30, 2017
Investments in Short-Term Time Deposits [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Interest rate used to estimate fair value |  | 5.30%
Long Term Notes Receivable From Municipalities [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Interest rate used to estimate fair value | 2.80% | 2.60%
Long-Term Debt [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Interest rate used to estimate fair value | 3.50% | 2.40%
Cash [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Cash and Cash Equivalents, Fair Value Disclosure | $ 61,050 | $ 79,822
Investments in Reverse Repurchase Agreements [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Cash and Cash Equivalents, Fair Value Disclosure | 185 | 1
Investments in Term Deposits with Foreign Banks [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Cash and Cash Equivalents, Fair Value Disclosure | 50,643 | $ 7,729
Restricted Investments in Term Deposits with Foreign Banks [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Cash and Cash Equivalents, Fair Value Disclosure | $ 3,769 |

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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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