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Electric Operating Revenue Narrative (Details) | Dec. 31, 2018 USD ($) utility MW | Dec. 31, 2017 USD ($) MW
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Contract with Customers, Asset and Liability [Roll Forward] |  |
Number of regulated utilities | utility | 2 |
Contract assets | $ | $ 0 |
Public Service Company of New Mexico |  |
Contract with Customers, Asset and Liability [Roll Forward] |  |
Expected exposure to market risk (in megawatts) | 65 | 65
Power to be sold to third party (in megawatts) | 36 | 36
Public Service Company of New Mexico | Contracts with Customers |  |
Contract with Customers, Asset and Liability [Roll Forward] |  |
Contract with customers, net | $ | $ 61,700,000 | $ 61,800,000
Palo Verde Nuclear Generating Station Unit 3 | Clean Air Act, SNCR | Public Service Company of New Mexico |  |
Contract with Customers, Asset and Liability [Roll Forward] |  |
Number of megawatts |  | 134

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