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Regulatory and Rate Matters - SJGS Abandonment Application, Fours Corners, PVNGS Leased Interest Abandonment Application, Summer Peak Resource Adequacy, COVID and Transportation Electrification Program (Details) $ in Thousands |  |  |  |  |  |  |  |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |  |
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Oct. 25, 2023 MW batteryStorageAgreement | Sep. 21, 2023 USD ($) | Aug. 18, 2023 USD ($) | Jul. 18, 2023 MW | Jan. 30, 2023 MW | Nov. 18, 2022 lease MW | Oct. 03, 2022 USD ($) | Jul. 29, 2022 USD ($) | Jul. 19, 2022 MW | Jun. 17, 2022 USD ($) | Jan. 08, 2021 USD ($) | Nov. 01, 2020 USD ($) | Nov. 30, 2020 USD ($) | Sep. 30, 2023 USD ($) | Sep. 30, 2022 USD ($) MW | Sep. 30, 2023 USD ($) | Mar. 31, 2023 MW | Sep. 30, 2022 USD ($) MW | Dec. 31, 2019 USD ($) proceeding | Dec. 31, 2022 USD ($) | Apr. 02, 2021 lease MW | Dec. 31, 2020 USD ($)
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Electric operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 505,851 | $ 729,888 | $ 1,527,084 |  | $ 1,673,736 |  |  |  |
Regulatory disallowance |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,700 |  |  |  |  |  |  |  |
Decrease in undepreciated leasehold improvements |  |  |  |  |  |  |  |  |  |  |  |  |  | 88,200 |  | 88,200 |  |  |  |  |  |
Increase in deferred regulatory assets |  |  |  |  |  |  |  |  |  |  |  |  |  | 88,200 |  | 88,200 |  |  |  |  |  |
Regulatory assets |  |  |  |  |  |  |  |  |  |  |  |  |  | 924,487 |  | 924,487 |  |  |  | $ 846,686 |  |
Regulatory liabilities |  |  |  |  |  |  |  |  |  |  |  |  |  | 764,360 |  | 764,360 |  |  |  | 755,202 |  |
Subsequent event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of battery storage agreements | batteryStorageAgreement | 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments for legal settlements |  |  |  |  |  |  |  | $ 19,800 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proposed rate credits |  |  | $ 115,000 |  |  |  |  |  |  |  |  |  |  |  |  | 115,000 |  |  |  |  |  |
Proposed rate credit payout period |  |  | 1 year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Securitization bonds, weighted-average maximum rate |  |  | 5.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Electric operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 350,334 | $ 597,337 | 1,118,741 |  | $ 1,312,800 |  |  |  |
Regulatory disallowance |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,700 |  |  |  |  |  |
Number of leases under which lease term was extended | lease |  |  |  |  |  | 5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 |
Potential loss on rate change |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 28,800 |  |  |  |  |  |
Number of megawatts, peak during period (in megawatts) | MW |  |  |  | 2,162 |  |  |  |  | 2,139 |  |  |  |  |  |  |  |  |  |  |  |  |
Grid modernization investment |  |  |  |  |  |  | $ 344,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Grid modernization, initial term |  |  |  |  |  |  | 6 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Grid modernization term |  |  |  |  |  |  | 11 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  |  |  |  |  |  |  |  |  |  |  |  | 846,107 |  | 846,107 |  |  |  | 763,941 |  |
Regulatory liabilities |  |  |  |  |  |  |  |  |  |  |  |  |  | 551,747 |  | 551,747 |  |  |  | 556,989 |  |
PNM | Four Corners |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Request issuance of energy transition bonds |  |  |  |  |  |  |  |  |  |  | $ 300,000 |  |  |  |  |  |  |  |  |  |  |
Forecasted undepreciated investment |  |  |  |  |  |  |  |  |  |  | 272,000 |  |  |  |  |  |  |  |  |  |  |
Plant decommissioning and coal mine reclamation costs |  |  |  |  |  |  |  |  |  |  | 4,600 |  |  |  |  |  |  |  |  |  |  |
Upfront financing costs |  |  |  |  |  |  |  |  |  |  | 7,300 |  |  |  |  |  |  |  |  |  |  |
Proceeds from securitization bonds |  |  |  |  |  |  |  |  |  |  | $ 16,500 |  |  |  |  |  |  |  |  |  |  |
Payments for relief from obligations |  |  |  |  |  |  |  |  |  |  |  | $ 75,000 | $ 15,000 |  |  |  |  |  |  |  |  |
Final payment for relief from obligations |  |  |  |  |  |  |  |  |  |  |  |  | $ 60,000 |  |  |  |  |  |  |  |  |
PNM | Four Corners | PNM |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Noncontrolling interest, ownership percentage by noncontrolling owners |  |  |  |  |  |  |  |  |  |  |  | 13.00% |  |  |  |  |  |  |  |  |  |
PNM | Deferred COVID-19 Costs | COVID-19 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  |  |  |  |  |  |  |  |  |  |  |  | 5,700 |  | 5,700 |  |  |  | 5,700 |  |
Regulatory liabilities |  |  |  |  |  |  |  |  |  |  |  |  |  | 900 |  | 900 |  |  |  | $ 900 |  |
PNM | Leased Interest Termination on January 15, 2023 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of leases under which lease term was extended | lease |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 |
PNM | Leased Interest Termination on January 15, 2023 | NMPRC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar generation capacity (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 104 |
PNM | Leased Interest Termination on January 15, 2024 | NMPRC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar generation capacity (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 |
PNM | Solar Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar generation capacity (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 300 |  |  | 300 |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW |  |  |  |  | 100 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | Battery Storage Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar generation capacity (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 300 |  |  | 300 |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW |  |  |  |  | 30 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | NM 2022 Rate Case |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Megawatt repurchase | MW |  |  |  |  |  | 64.1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | Firm Power Purchases |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 420 |  |  |  |  |
PNM | Firm Capacity |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40 |  |  |  |  |
PNM | Solar Agreement One | Subsequent event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW | 100 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | Solar Agreement Two | Subsequent event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW | 60 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | Battery Storage Agreement One | Subsequent event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW | 100 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | Battery Storage Agreement Two | Subsequent event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW | 100 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | Battery Storage Agreement Three | Subsequent event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW | 50 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNMR and PNM | New Mexico Public Regulation Commission+ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Electric operating revenues |  | $ (115,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory liability |  |  |  |  |  |  |  |  |  |  |  |  |  | 115,000 |  | 115,000 |  |  |  |  |  |
Regulatory asset, reversal |  |  |  |  |  |  |  |  |  |  |  |  |  | (2,300) |  | $ (2,300) |  |  |  |  |  |
Regulatory disallowance |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,300 |  |  |  |  |  |  |  |
San Juan Generating Station | PNM |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Request issuance of energy transition bonds |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 361,000 |  |  |
Forecasted undepreciated investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 283,000 |  |  | $ 361,000
Plant decommissioning and coal mine reclamation costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 28,600 |  |  |
Upfront financing costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 9,600 |  |  |
Severance costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 20,000 |  |  |
Proceeds from securitization bonds |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 19,800 |  |  |
Number of proceedings | proceeding |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |
Number of recommendations | proceeding |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |
San Juan Generation Station, Unit 1 | PNM |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual rate credits |  |  |  |  |  |  |  |  |  | $ 21,100 |  |  |  |  |  |  |  |  |  |  |  |
San Juan Generating Station, Unit 4 | PNM |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual rate credits |  |  |  |  |  |  |  |  |  | $ 98,300 |  |  |  |  |  |  |  |  |  |  |  |
Number of days to transfer payment |  |  |  |  |  |  |  |  |  | 30 days |  |  |  |  |  |  |  |  |  |  |  |

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