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Pension and Other Postretirement Benefits - Narrative (Details) - USD ($) |  | 12 Months Ended
--- | --- | ---
Jan. 01, 2018 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
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 |  |
Expected employer disbursements for next fiscal year |  | $ 3,200,000 |  |
Expected employer disbursements by employer in year 2 through year 5 |  | $ 11,900,000 |  |
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% |  |
Public Service Company of New Mexico |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Actuarial gains (losses) recorded as regulatory assets |  | $ 5,700,000 |  |
Texas-New Mexico Power Company |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Actuarial gains (losses) recorded as regulatory assets |  | $ 1,000,000 |  |
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 (as a percent) |  | 1.00% |  |
Expected employer contributions to pension plans |  | $ 0 |  |
Pension Plan | Minimum |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Weighted average discount rate related to anticipated contributions |  | 2.90% |  |
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 | Public Service Company of New Mexico |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Expected return on plan assets |  | 5.50% | 5.90% | 6.86%
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year |  | $ 5,200,000 |  |
Rate of return for retirement plan |  | 5.80% |  |
Actuarial gains (losses) recorded as regulatory assets |  | $ 23,632,000 |  |
Employer contributions |  | $ 0 | $ 0 |
Pension Plan | Texas-New Mexico Power Company |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Expected return on plan assets |  | 5.50% | 5.90% | 6.90%
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year |  | $ 600,000 |  |
Rate of return for retirement plan |  | 4.68% |  |
Actuarial gains (losses) recorded as regulatory assets |  | $ (3,133,000) |  |
Employer contributions |  | $ 0 | $ 0 |
Pension Plan | Texas-New Mexico Power Company | Equity Securities |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Investment allocation targets |  | 16.00% |  |
Pension Plan | Texas-New Mexico Power Company | Fixed income |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Investment allocation targets |  | 70.00% |  |
Pension Plan | Texas-New Mexico Power Company | 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 | Public Service Company of New Mexico |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Expected return on plan assets |  | 4.75% | 7.00% | 7.20%
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year |  | $ 900,000 |  |
Expected long-term return resulting from effect of one-percentage point increase (as a percent) |  | 5.20% |  |
Employer matching contribution, maximum | 5.00% |  |  |
Employer contributions |  | $ 2,709,000 | $ 3,256,000 |
Other Postretirement Benefits | Texas-New Mexico Power Company |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Expected return on plan assets |  | 3.80% | 5.60% | 5.80%
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year |  | $ 100,000 |  |
Expected long-term return resulting from effect of one-percentage point increase (as a percent) |  | 2.30% |  |
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 |
Executive Retirement Program | Public Service Company of New Mexico |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Actuarial gains (losses) recorded as regulatory assets |  | 657,000 |  |
Expected disbursements by employer |  | 1,300,000 | 1,400,000 |
Executive Retirement Program | Texas-New Mexico Power Company |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |
Actuarial gains (losses) recorded as regulatory assets |  | 211,000 |  |
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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