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Electric Operating Revenues - Narrative (Details) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2021 USD ($) utility | Jun. 30, 2020 USD ($) | Jun. 30, 2021 USD ($) utility | Jun. 30, 2020 USD ($) | Dec. 31, 2020 USD ($)
Disaggregation of Revenue [Line Items] |  |  |  |  |
Number of regulated utilities | utility | 2 |  | 2 |  |
Accounts receivable, allowance for credit loss, period increase (decrease) | $ 800,000 | $ 400,000 | $ 2,400,000 | $ 700,000 |
Contract assets | 0 |  | 0 |  | $ 0
Texas-New Mexico Power Company |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |
Regulatory assets | 1,000,000.0 |  | 1,000,000.0 |  |
PNM |  |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |  |
Accounts receivable | $ 89,200,000 |  | $ 89,200,000 |  | $ 86,200,000

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