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Financial Instruments Fair Value Hedges and Cash Flow Hedges (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2017 | Jun. 30, 2016
Effect of Fair Value Hedges on Results of Operations [Abstract] |  |  |  |
Commodity contracts | $ 0 | $ (22,146) | $ (9,567) | $ (11,808)
Fair value adjustment for natural gas inventory designated as the hedged item | 0 | 35,630 | 12,858 | 29,852
Total (increase) decrease to purchased gas cost | 0 | 13,484 | 3,291 | 18,044
Basis ineffectiveness | 0 | (684) | (597) | (1,490)
Timing ineffectiveness | 0 | 14,168 | 3,888 | 19,534
Summary of Cash Flow Hedge Activity [Abstract] |  |  |  |
Gain (loss) reclassified from AOCI into purchased gas cost for effective portion of commodity contracts | 0 | (12,347) | (2,612) | (48,015)
Gain (loss) arising from ineffective portion of commodity contracts | 0 | 66 | 111 | 84
Gain (Loss) on Discontinuation of Cash Flow Hedge | 0 | 0 | 10,579 | 0
Total impact on purchased gas cost | 0 | (12,281) | 8,078 | (47,931)
Loss on settled Treasury Lock agreements reclassified from AOCI into interest expense | (177) | (137) | (450) | (410)
Total Impact from Cash Flow Hedges | $ (177) | $ (12,418) | $ 7,628 | $ (48,341)

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- Definition The amount of net gains or losses on a cash flow hedge reclassified in the period to earnings from accumulated other comprehensive income. + References No definition available. + Details
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- Definition The amount of net gains or losses on a cash flow hedge reclassified to purchased gas cost from accumulated other comprehensive income or representing the ineffective portion of the hedge. + References No definition available. + Details
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- Definition The amount of net gains or losses on a cash flow hedge reclassified in the period to purchased gas cost from accumulated other comprehensive income + References No definition available. + Details
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- Definition Gain (loss) recognized in earnings during the reporting period representing the amount of the fair value hedges' ineffectiveness due to a difference in basis. + References No definition available. + Details
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- Definition Gain (loss) recognized in earnings during the reporting period representing the amount of the fair value hedges' ineffectiveness due to a difference in timing. + References No definition available. + Details
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- Definition Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 25 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986 + Details
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- Definition Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 25 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986 + Details
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- Definition The net gain (loss) recognized in earnings during the reporting period representing the amount of the cash flow hedges' ineffectiveness. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959 + Details
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- Definition The amount of net gain (loss) reclassified into earnings in the period when cash flow hedge is discontinued because it is probable that the original forecasted transactions will not occur by the end of the original period or an additional two month time period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994 + Details
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- Definition Total amount of gain (loss) derived from fair value hedges recognized in earnings in the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959 + Details
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- Definition The amount of net gains or losses on interest rate cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income upon the hedged transaction affecting earnings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959 + Details
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