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Financial Instruments Other Comprehensive Income (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | [1] | Mar. 31, 2018 | Mar. 31, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract] |  |  |  |  |  |
Interest rate agreements fair value |  | $ 21,786 | $ 4,144 | $ 20,454 | $ 95,271 | [1]
Forward commodity contracts fair value | [2] | 0 | 0 | 0 | 9,847 | [1]
Interest rate agreements |  | 458 | 86 | 835 | 173 | [1]
Forward commodity contracts | [2] | 0 | 0 | 0 | (4,865) | [1]
Total other comprehensive income (loss) from hedging, net of tax |  | 22,244 | $ 4,230 | 21,289 | $ 100,426 | [1]
Regulated Segments Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate |  |  |  |  | 37.00% |
Nonregulated Segment Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate |  |  |  |  | 39.00% |
Expected Earnings [Line Items] |  |  |  |  |  |
Expected Recognition in Earnings of Deferred Gain (Losses), Interest Rate Agreements |  | (49,114) |  | (49,114) |  |
Next Twelve Months [Member] |  |  |  |  |  |
Expected Earnings [Line Items] |  |  |  |  |  |
Expected Recognition in Earnings of Deferred Gain (Losses), Interest Rate Agreements |  | (1,833) |  | (1,833) |  |
Thereafter [Member] |  |  |  |  |  |
Expected Earnings [Line Items] |  |  |  |  |  |
Expected Recognition in Earnings of Deferred Gain (Losses), Interest Rate Agreements |  | $ (47,281) |  | $ (47,281) |  |
[1] | Utilizing an income tax rate ranging from 37 percent to 39 percent based on the effective rates in each taxing jurisdiction for the three and six-month period ended March 31, 2017.
[2] | Due to the sale of AEM, these amounts are included in income from discontinued operations

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