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Financial Instruments Descriptions (Details) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Jun. 30, 2016 USD ($) | Jun. 30, 2017 USD ($) MMcf | Jun. 30, 2016 USD ($)
General Discussion Of Derivative Instruments And Hedging Activities [Abstract] |  |  |
Minimum Hedge Percentage Of Anticipated Heating Season Gas |  | 25.00% |
Maximum Hedge Percentage Of Anticipated Heating Season Gas |  | 50.00% |
Hedge Percentage Of Actual Heating Season Gas |  | 27.00% |
Hedge Volume Of Actual Heating Season Gas | MMcf |  | 16,200 |
Gain on Discontinuation of Cash Flow Hedge |  | $ 10.6 |
Accumulated Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Interest Rate Agreements, Realized Gain (Loss), Net of Tax |  | (41.5) |
Gain (Loss) On Hedge Ineffectiveness | $ 13.6 | $ 3.4 | $ 18.1
Regulated Segments Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate |  | 37.00% | 37.00%
Nonregulated Segment Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate |  | 39.00% | 39.00%
Gain (Loss) On Derivative Instruments Not Designated Hedges Net Pretax | $ 1.9 | $ 6.8 | $ (2.8)
Interest Rate Hedges, Senior Notes 2019 Issuance [Member] |  |  |
Derivative [Line Items] |  |  |
Notional Amount of Interest Rate Cash Flow Hedge Derivatives |  | 450.0 |
Anticipated Debt Issuance, Amount |  | $ 450.0 |
Derivative, Average Forward Interest Rate |  | 3.78% |

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- Definition Net realized gains and losses in accumulated other comprehensive income from interest rate agreements designated and qualifying as the effective portion of cash flow hedges. + References No definition available. + Details
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- Definition Anticipated debt issuance amount of future debt issuance. + References No definition available. + Details
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- Definition Gain or loss recognized in earnings during the reporting period representing the amount of the hedges' ineffectiveness for fair value and cash flow hedges. + References No definition available. + Details
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- Definition Actual percentage of heating season gas purchases hedged using financial instruments. + References No definition available. + Details
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- Definition Actual volume of heating season gas purchases hedged using financial instruments. + References No definition available. + Details
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- Definition Maximum anticipated percentage of heating season gas purchases hedged using financial instruments. + References No definition available. + Details
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- Definition Minimum anticipated percentage of heating season gas purchases hedged using financial instruments. + References No definition available. + Details
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- Definition The domestic federal statutory tax rate applicable under enacted tax laws to the Nonregulated operations pretax income from continuing operations for the period. The "statutory" tax rate shall be the regular tax rate if there are alternative tax systems. + References No definition available. + Details
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- Definition The domestic federal statutory tax rate applicable under enacted tax laws to the Regulated operations pretax income from continuing operations for the period. The "statutory" tax rate shall be the regular tax rate if there are alternative tax systems. + References No definition available. + Details
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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments. + 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 (e) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959 + Details
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- Definition The amount of gain 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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