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Pension and Other Postretirement Benefit Plans - Narrative (Details) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2022 | Sep. 30, 2021
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 | 600,000 |  | $ 600,000 |
Pension Plan | PNM | Maximum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Assumptions used calculating net periodic benefit cost, discount rate |  |  | 5.00% |
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 |  |  | 5.00% |
OPEB Plan | PNM |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions by employer |  |  | $ 0 | 0
Disbursements by employer | 900,000 | $ 1,000,000 | 2,400,000 | 2,700,000
Disbursements by employer, year one through four | 15,100,000 |  | 15,100,000 |
Estimated disbursement by employer, current year |  |  | 3,400,000 |
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 |  | 0 |
Executive Retirement Program | PNM |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions by employer | 400,000 | $ 300,000 | 1,000,000 | 1,100,000
Disbursements by employer, year one through four | 5,800,000 |  | 5,800,000 |
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 |  | 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 |  |  | $ 100,000 | $ 100,000

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