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Fair Value of Derivative and Other Financial Instruments - Narrative (Details) |  |  |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 18, 2022 MW | Feb. 17, 2022 MW | Nov. 15, 2015 power_purchase_agreement | Jun. 30, 2022 MW | Dec. 31, 2022 USD ($) MW | Mar. 31, 2021 USD ($) | Dec. 31, 2021 USD ($) power_purchase_agreement | Dec. 31, 2022 USD ($) MWh MW | Dec. 31, 2021 USD ($) MWh MW power_purchase_agreement | Dec. 31, 2020 USD ($) | May 31, 2022 MW | Jan. 01, 2018 MW
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of purchase power agreements | power_purchase_agreement |  |  |  |  |  |  | 3 |  |  |  |  |
Contract in a net liability position |  |  |  |  | $ 15,300,000 |  |  | $ 15,300,000 |  |  |  |
Cash collateral |  |  |  |  | 0 |  |  | 0 |  |  |  |
Net exposure |  |  |  |  | $ 13,100,000 |  |  | 13,100,000 |  |  |  |
Available for sale securities realized impairment losses |  |  |  |  |  |  |  | $ (25,800,000) | $ 700,000 | $ (3,200,000) |  |
Minimum |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Investment allocation targets distribution period |  |  |  |  |  |  |  | 10 years |  |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Investment allocation targets distribution period |  |  |  |  |  |  |  | 15 years |  |  |  |
Equity Securities | Pension Plan |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Investment allocation targets |  |  |  |  | 35.00% |  |  | 35.00% |  |  |  |
Alternative Investments | Pension Plan |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Investment allocation targets |  |  |  |  | 15.00% |  |  | 15.00% |  |  |  |
Fixed income | Pension Plan |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Investment allocation targets |  |  |  |  | 50.00% |  |  | 50.00% |  |  |  |
PNM |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of purchase power agreements | power_purchase_agreement |  |  | 2 |  |  |  |  |  | 3 |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW | 65 | 327 |  |  |  |  |  |  |  |  |  |
Expected exposure to market risk (in megawatts) | MW |  |  |  |  | 65 |  |  | 65 |  |  |  | 65
Power to be sold to third party (in megawatts) | MW |  |  |  |  | 36 |  |  | 36 |  |  | 50 | 36
Amounts recognized for the legal right to reclaim cash collateral |  |  |  |  | $ 0 |  | $ 0 | $ 0 | $ 0 |  |  |
Amounts posted as cash collateral under margin arrangements |  |  |  |  | 10,500,000 |  | 500,000 | 10,500,000 | 500,000 |  |  |
Obligations to return cash collateral |  |  |  |  | 200,000 |  | 900,000 | $ 200,000 | $ 900,000 |  |  |
Number Of Purchase Power Agreement Not Considered Derivatives | power_purchase_agreement |  |  |  |  |  |  |  |  | 2 |  |  |
PNM | Natural Gas Cost | Unusual Weather |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cost of energy and production costs |  |  |  |  |  | $ 20,000,000 |  |  |  |  |  |
PNM | Electricity, Purchased | Unusual Weather |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cost of energy and production costs |  |  |  |  |  | $ 8,000,000 |  |  |  |  |  |
PNM | Commodity Contract | Fair Value Hedging |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Power-related contracts (MWh) | MWh |  |  |  |  |  |  |  | 432,200 | 122,400 |  |  |
PNM | Commodity Contract | Designated as hedging instrument |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Derivative asset, fair value, gross liability |  |  |  |  | 0 |  | 500,000 | $ 0 | $ 500,000 |  |  |
Derivative asset, fair value, gross asset |  |  |  |  | 0 |  | 500,000 | 0 | 500,000 |  |  |
Other current assets |  |  |  |  | 9,780,000 |  | 684,000 | 9,780,000 | 684,000 |  |  |
Current derivative liability |  |  |  |  | 19,209,000 |  | 2,275,000 | 19,209,000 | 2,275,000 |  |  |
PNM | Fuel and purchased power costs | Commodity Contract | Designated as hedging instrument |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Other current assets |  |  |  |  | 9,800,000 |  | 200,000 | 9,800,000 | 200,000 |  |  |
Current derivative liability |  |  |  |  | $ 19,200,000 |  | 1,800,000 | $ 19,200,000 | $ 1,800,000 |  |  |
PNM | Portfolio One |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW |  |  |  | 35 | 270 |  |  | 85 | 85 |  |  |
PNM | Portfolio Two |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW |  |  |  | 25 |  |  |  | 150 | 40 |  |  |
PNM | Portfolio Three |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW |  |  |  |  | 40 |  |  | 40 | 150 |  |  |
PNM | Tri-State |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Power to be sold to third party (in megawatts) | MW |  |  |  |  | 100 |  |  | 100 |  |  |  |
Texas-New Mexico Power Company |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cost of energy and production costs |  |  |  |  |  |  |  | $ 123,928,000 | $ 113,067,000 | $ 102,074,000 |  |
Texas-New Mexico Power Company | Equity Securities | Pension Plan |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Investment allocation targets |  |  |  |  | 16.00% |  |  | 16.00% |  |  |  |
Texas-New Mexico Power Company | Alternative Investments | Pension Plan |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Investment allocation targets |  |  |  |  | 14.00% |  |  | 14.00% |  |  |  |
Texas-New Mexico Power Company | Fixed income | Pension Plan |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Investment allocation targets |  |  |  |  | 70.00% |  |  | 70.00% |  |  |  |
Measured on a recurring basis | PNM |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Debt securities, available-for-sale |  |  |  |  | $ 417,476,000 |  | 463,126,000 | $ 417,476,000 | 463,126,000 |  |  |
Nuclear Decommissioning Trust | Measured on a recurring basis | PNM |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Debt securities, available-for-sale |  |  |  |  | 325,300,000 |  | 394,500,000 | 325,300,000 | 394,500,000 |  |  |
Mine Reclamation Trust | Measured on a recurring basis | PNM |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Debt securities, available-for-sale |  |  |  |  | 77,500,000 |  | 68,600,000 | 77,500,000 | 68,600,000 |  |  |
SJGS Decommissioning Trust | Measured on a recurring basis | PNM |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Debt securities, available-for-sale |  |  |  |  | $ 14,700,000 |  | $ 0 | $ 14,700,000 | $ 0 |  |  |

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