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Financial Instruments and Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Sep. 30, 2017
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Financial liability on recurring basis | $ 0 |
Investments in Short-Term Time Deposits [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Interest rate used to estimate fair value | 5.60% | 5.30%
Long Term Notes Receivable From Municipalities [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Interest rate used to estimate fair value | 2.50% | 2.60%
Long-Term Debt [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Interest rate used to estimate fair value | 2.30% | 2.40%

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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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- Definition Fair value of financial and nonfinancial obligations. + 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 (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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