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Pension and Other Postretirement Benefits - Narrative (Details) - USD ($) |  | 12 Months Ended
--- | --- | ---
Jan. 01, 2018 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Expected return on plan assets |  | 4.00% |  |
Amortization of gains and losses that are outside the corridor |  | 5 years |  |
Maximum annual contributions per employee |  | 75.00% |  |
Employer matching contribution, percent of employees' gross pay |  | 6.00% |  |
Minimum |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Non-matching contribution of eligible compensation based on eligible employee's age |  | 3.00% |  |
Maximum |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Non-matching contribution of eligible compensation based on eligible employee's age |  | 10.00% |  |
PNM |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Rate of return |  | 10.20% |  |
TNMP |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Rate of return |  | 7.22% |  |
Pension Plan |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Expected long-term return resulting from effect of 1% change |  | 1.00% |  |
Expected long-term return resulting from effect of one-percentage point increase |  | 1.00% |  |
Expected future employer contributions, year two through four |  | $ 0 |  |
Expected future employer contributions, after year four |  | $ 200,000 |  |
Weighted average discount rate related to anticipated contributions |  | 5.47% |  |
Pension Plan | Equity Securities |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Investment allocation targets |  | 35.00% |  |
Pension Plan | Fixed income |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Investment allocation targets |  | 50.00% |  |
Pension Plan | Alternative Investments |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Investment allocation targets |  | 15.00% |  |
Pension Plan | PNM |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Expected return on plan assets |  | 6.30% | 5.50% | 5.50%
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year |  | $ 4,500,000 |  |
Actuarial gains (losses) recorded as regulatory assets and liabilities |  | 6,193,000 |  |
Employer contributions |  | $ 0 | $ 0 |
Pension Plan | TNMP |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Expected return on plan assets |  | 5.50% | 4.40% | 5.50%
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year |  | $ 500,000 |  |
Actuarial gains (losses) recorded as regulatory assets and liabilities |  | (1,005,000) |  |
Employer contributions |  | $ 0 | $ 0 |
Pension Plan | TNMP | Equity Securities |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Investment allocation targets |  | 16.00% |  |
Pension Plan | TNMP | Fixed income |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Investment allocation targets |  | 70.00% |  |
Pension Plan | TNMP | Alternative Investments |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Investment allocation targets |  | 14.00% |  |
Other Postretirement Benefits |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Expected long-term return resulting from effect of 1% change |  | 1.00% |  |
Other Postretirement Benefits | Equity Securities |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Investment allocation targets |  | 30.00% |  |
Other Postretirement Benefits | Fixed income |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Investment allocation targets |  | 70.00% |  |
Other Postretirement Benefits | PNM |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Expected return on plan assets |  | 5.90% | 4.75% | 4.75%
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year |  | $ 800,000 |  |
Rate of return |  | 11.40% |  |
Actuarial gains (losses) recorded as regulatory assets and liabilities |  | $ (4,400,000) |  |
Employer matching contribution, maximum | 5.00% |  |  |
Employer contributions |  | $ 157,000 | $ 2,617,000 |
Other Postretirement Benefits | TNMP |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Expected return on plan assets |  | 4.70% | 3.80% | 3.80%
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year |  | $ 100,000 |  |
Rate of return |  | 2.00% |  |
Actuarial gains (losses) recorded as regulatory assets and liabilities |  | $ (100,000) |  |
Effect of 1%-point change in assumed health care cost trend rates on net periodic expense and APBO |  | 0 |  |
Employer contributions |  | 0 | $ 0 |
Other Postretirement Benefits | PNM and TNMP |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Employer contributions |  | 0 | 0 |
Expected employer contributions in fiscal year through year 5 |  | 0 | 0 |
Expected employer disbursements for next fiscal year |  | 200,000 |  |
Expected employer disbursements by employer in year 2 through year 5 |  | 10,100,000 |  |
Executive Retirement Program | PNM |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Actuarial gains (losses) recorded as regulatory assets and liabilities |  | (411,000) |  |
Expected disbursements by employer |  | 1,300,000 | 1,300,000 |
Executive Retirement Program | TNMP |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Actuarial gains (losses) recorded as regulatory assets and liabilities |  | (13,000) |  |
Expected disbursements by employer |  | $ 100,000 | $ 100,000 |
Non-US | Pension Plan | Equity Securities |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Investment allocation targets |  | 13.00% |  |

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