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Electric Operating Revenues - Narrative (Details) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2020 USD ($) MW | Dec. 31, 2019 USD ($) | Dec. 31, 2017 MW
Contract with Customers, Asset and Liability [Roll Forward] |  |  |
Capitalized contract cost, amortization period (in years) | 5 years |  |
Contract assets | $ 0 |  |
Public Service Company of New Mexico |  |  |
Contract with Customers, Asset and Liability [Roll Forward] |  |  |
Expected exposure to market risk (in megawatts) | MW | 65 |  | 65
Power to be sold to third party (in megawatts) | MW | 36 |  | 36
Contract with customers, net | $ 86,200,000 | $ 59,300,000 |
Accounts receivable, credit loss expense (reversal) | $ 7,200,000 |  |

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