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Fair Value of Derivative and Other Financial Instruments - Sale of Power (Details) - PNMR and PNM [Member] - Palo Verde Nuclear Generating Station Unit 3 [Member] | Dec. 31, 2017 $ / MWh | Dec. 31, 2016 MW
--- | --- | ---
Sale of Power [Line Items] |  |
Number of megawatts not included in retail rates (in megawatts) | MW |  | 134
Percentage of electric power plant output sold or contracted to sell |  | 100.00%
Commodity Contract [Member] | Subsequent Event [Member] |  |
Sale of Power [Line Items] |  |
Derivative, average forward price (in dollars per megawatt hour) | $ / MWh | 29 |

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- Definition Percentage of Electric Power Plant Output Sold through 2017 + References No definition available. + Details
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- Definition Public Utilities, Number of Megawatts Nuclear Generation + References No definition available. + Details
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- Definition Sale of Power [Line Items] + References No definition available. + Details
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- Definition The average forward price on the group of price risk forward or futures contracts, such as gas futures contracts. + References No definition available. + Details
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- Details
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- Details
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- Details
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- Details
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