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Pension and Other Postretirement Benefits - Schedule of Fair Value of Plan Assets, and Funded Status of the Plans of PBO, APBO and Executive Retirement Programs (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |
Accrued pension liability and postretirement benefit cost | $ 23,065 | $ 21,429 |
PNM |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |
Accrued pension liability and postretirement benefit cost | 22,067 | 19,949 |
PNM | Pension Plan |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Balance at beginning of year | 418,657 | 433,645 |
Service cost | 0 | 0 | $ 0
Interest cost | 21,709 | 23,653 | 16,857
Actuarial (gain) loss | (6,063) | 4,290 |
Benefits paid | (40,942) | (42,931) |
Settlements | 0 | 0 |
Balance at end of year | 393,361 | 418,657 | 433,645
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |
Fair value of plan assets at beginning of year | 407,211 | 410,463 |
Actual return on plan assets | 12,884 | 39,679 |
Employer contributions | 1 | 0 |
Benefits paid | (40,942) | (42,931) |
Settlements | 0 | 0 |
Fair value of plan assets at end of year | 379,154 | 407,211 | 410,463
Funded status – asset (liability) for pension benefits | (14,207) | (11,446) |
PNM | Other Postretirement Benefits |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Balance at beginning of year | 46,217 | 49,950 |
Service cost | 0 | 0 | 10
Interest cost | 2,387 | 2,703 | 1,914
Participant contributions | 1,463 | 1,592 |
Actuarial (gain) loss | (2,205) | (1,608) |
Benefits paid | (6,261) | (6,420) |
Curtailment loss | 0 | 0 | 836
Balance at end of year | 41,601 | 46,217 | 49,950
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |
Fair value of plan assets at beginning of year | 73,392 | 70,301 |
Actual return on plan assets | 3,216 | 7,762 |
Employer contributions | 193 | 157 |
Participant contributions | 1,463 | 1,592 |
Benefits paid | (6,261) | (6,420) |
Fair value of plan assets at end of year | 72,003 | 73,392 | 70,301
Funded status – asset (liability) for pension benefits | 30,402 | 27,175 |
PNM | Executive Retirement Program |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Balance at beginning of year | 9,714 | 10,042 |
Service cost | 0 | 0 | 0
Interest cost | 496 | 540 | 362
Actuarial (gain) loss | (47) | 411 |
Benefits paid | (1,132) | (1,279) |
Balance at end of year | 9,031 | 9,714 | 10,042
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |
Less current liability | 1,171 | 1,210 |
Accrued pension liability and postretirement benefit cost | 7,860 | 8,504 |
TNMP |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |
Accrued pension liability and postretirement benefit cost | 998 | 1,480 |
TNMP | Pension Plan |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Balance at beginning of year | 42,582 | 43,961 |
Service cost | 0 | 0 | 0
Interest cost | 2,214 | 2,402 | 1,720
Actuarial (gain) loss | (2,047) | 1,261 |
Benefits paid | (3,526) | (5,042) |
Settlements | 0 | 0 |
Balance at end of year | 39,223 | 42,582 | 43,961
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |
Fair value of plan assets at beginning of year | 41,353 | 43,447 |
Actual return on plan assets | 247 | 2,948 |
Employer contributions | 151 | 0 |
Benefits paid | (3,526) | (5,042) |
Settlements | 0 | 0 |
Fair value of plan assets at end of year | 38,225 | 41,353 | 43,447
Funded status – asset (liability) for pension benefits | (998) | (1,229) |
TNMP | Other Postretirement Benefits |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Balance at beginning of year | 7,331 | 7,705 |
Service cost | 21 | 21 | 38
Interest cost | 385 | 425 | 307
Participant contributions | 357 | 359 |
Actuarial (gain) loss | (147) | (282) |
Benefits paid | (1,193) | (897) |
Curtailment loss | 0 | 0 |
Balance at end of year | 6,754 | 7,331 | 7,705
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |
Fair value of plan assets at beginning of year | 8,353 | 8,718 |
Actual return on plan assets | 25 | 173 |
Employer contributions | 0 | 0 |
Participant contributions | 357 | 359 |
Benefits paid | (1,193) | (897) |
Fair value of plan assets at end of year | 7,542 | 8,353 | 8,718
Funded status – asset (liability) for pension benefits | 788 | 1,022 |
TNMP | Executive Retirement Program |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Balance at beginning of year | 316 | 344 |
Service cost | 0 | 0 | 0
Interest cost | 15 | 18 | 11
Actuarial (gain) loss | (314) | 13 |
Benefits paid | (17) | (59) |
Balance at end of year | 0 | 316 | $ 344
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |
Less current liability | 0 | 64 |
Accrued pension liability and postretirement benefit cost | $ 0 | $ 252 |

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