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Pension and Other Postretirement Benefit Plans - Narrative (Details) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
Pension Plan | PNM |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions by employer |  |  | $ 0 | $ 0
Estimated employer contributions for remainder of fiscal year through year four | $ 0 |  | 0 |
Estimated future contributions, year five | 400,000 |  | $ 400,000 |
Pension Plan | PNM | Maximum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Assumptions used calculating net periodic benefit cost, discount rate |  |  | 5.70% |
Pension Plan | Texas-New Mexico Power Company |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions by employer |  |  | $ 0 | 0
Estimated employer contributions for remainder of fiscal year through year four | 0 |  | $ 0 |
Pension Plan | Texas-New Mexico Power Company | Maximum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Assumptions used calculating net periodic benefit cost, discount rate |  |  | 5.80% |
OPEB Plan | PNM |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions by employer |  |  | $ 0 | 0
Disbursements by employer | 100,000 | $ 900,000 | 100,000 | 2,400,000
Disbursements by employer, year one through four |  |  | 9,000,000 |
Estimated disbursement by employer, current year |  |  | 200,000 |
OPEB Plan | Texas-New Mexico Power Company |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions by employer | 0 | 0 | 0 | 0
Disbursements by employer, year one through four |  |  | 0 |
Executive Retirement Program | PNM |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions by employer | 400,000 | 400,000 | 1,000,000 | 1,000,000
Disbursements by employer, year one through four |  |  | 4,500,000 |
Estimated disbursement by employer, current year |  |  | 1,300,000 |
Executive Retirement Program | Texas-New Mexico Power Company |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Disbursements by employer, year one through four |  |  | 200,000 |
Estimated disbursement by employer, current year |  |  | 100,000 |
Executive Retirement Program | Texas-New Mexico Power Company | Maximum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions by employer | $ 0 | $ 0 | $ 0 | $ 0

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