| **Long Term Debt Instruments**              | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
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| **Long-term Debt, Unclassified [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| Long-Term Debt Instruments                  | Long-Term Debt InstrumentsThe NCUC approved debt and equity issuances under an effective debt and equity shelf registration statement up to $1 billion through June 6, 2017. As of July 31, 2016, we have $244.1 million remaining for debt and equity issuances as approved by the NCUC, including the issuance of debt discussed below. For further information on equity transactions, see Note 7 to the condensed consolidated financial statements in this Form 10-Q. Unless otherwise specified at the time such securities are offered for sale, the net proceeds from the sale of the securities will be used to finance capital expenditures, to repay outstanding short-term, unsecured notes under our commercial paper (CP) program, to refinance other indebtedness, to repurchase our common stock, to pay dividends and for general corporate purposes.On June 6, 2016, we repaid $40 million of our 2.92% senior notes at maturity.On July 28, 2016, we issued $300 million of unsecured senior notes maturing November 1, 2046 with an interest rate of 3.64% and at a discount of .122% or $366,000 under the registration statement in effect noted above. We have the option to redeem all or part of the notes before May 1, 2046, at a redemption price equal to the greater of a) 100% of the principal amount of the notes to be redeemed, and b) the sum of the present values of the remaining scheduled payments of principal and interest on the notes to be redeemed, discounted to the date of redemption on a semi-annual basis at the Treasury Rate as defined in the indenture, as supplemented, plus 25 basis points and any accrued and unpaid interest to the date of redemption. We have the option to redeem all or part of the notes on or after May 1, 2046, at 100% of the principal amount plus any accrued and unpaid interest to the date of redemption. We used the net proceeds of $297 million from this issuance to finance capital expenditures, to repay outstanding short-term, unsecured notes under our CP program and for general corporate purposes.Our long-term debt as of July 31, 2016 and October 31, 2015 is presented below.In thousandsJuly 31, 2016 October 31, 2015Principal$1,835,000 $1,575,000Unamortized debt issuance expenses and discounts(13,816) (11,323)Total1,821,184 1,563,677Less current maturities— 40,000Total long-term debt$1,821,184 $1,523,677We are subject to default provisions related to our long-term debt and short-term borrowings. Failure to satisfy any of the default provisions may result in total outstanding issues of debt becoming due. There are cross default provisions in all of our debt agreements. |

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| - References
No definition available.
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| - Definition
The entire disclosure for long-term debt.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
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