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Pension and Other Postretirement Benefit Plans - Narrative (Details) - USD ($) | 3 Months Ended
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Mar. 31, 2024 | Mar. 31, 2023
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 |
Pension Plan | PNM | Maximum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Assumptions used calculating net periodic benefit cost, discount rate | 5.50% |
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 |
Estimated future contributions, year five | $ 200,000 |
Pension Plan | Texas-New Mexico Power Company | Maximum |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Assumptions used calculating net periodic benefit cost, discount rate | 5.50% |
OPEB Plan | PNM |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Contributions by employer | $ 0 | 0
Disbursements by employer | 100,000 | 800,000
Disbursements by employer, year one through four | 10,100,000 |
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
Disbursements by employer, year one through four | 0 |
Executive Retirement Program | PNM |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Contributions by employer | 300,000 | 100,000
Disbursements by employer, year one through four | 4,400,000 |
Estimated disbursement by employer, current year | 1,200,000 |
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 | $ 100,000 | $ 100,000

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