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Regulatory and Rate Matters - SJGS, Fours Corners and PVNGS Leased Interest Abandonment Applications (Details) $ in Thousands |  |  |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 18, 2022 MW | Feb. 17, 2022 MW | Apr. 02, 2021 lease MW | Feb. 03, 2021 | Jan. 08, 2021 USD ($) | Nov. 01, 2020 USD ($) | Jul. 01, 2019 USD ($) | Nov. 30, 2020 USD ($) | Mar. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) MW power_purchase_agreement | Dec. 31, 2021 USD ($) power_purchase_agreement MW | Apr. 14, 2022 MW | Dec. 18, 2020 USD ($) | Nov. 13, 2020 MW | Sep. 28, 2020 USD ($) | Jul. 29, 2020 MW | Mar. 31, 2020 USD ($) | Feb. 21, 2020 USD ($)
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory time frame for proposed PPAs and battery storage agreements |  |  | 6 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of purchase power agreements | power_purchase_agreement |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |  |
Regulatory assets |  |  |  |  |  |  |  |  | $ 511,639 | $ 514,258 | $ 514,258 |  |  |  |  |  |  |
Regulatory liabilities |  |  |  |  |  |  |  |  | 845,701 | 841,393 | $ 841,393 |  |  |  |  |  |  |
COVID-19 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Temporary mandatory moratorium on disconnection period |  |  |  | 100 days |  |  |  |  |  |  |  |  |  |  |  |  |  |
Disconnection transition period |  |  |  | 90 days |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar generation capacity (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 650 |  |
Number of megawatts in battery storage facilities (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 300 |  |
Number of purchase power agreements | power_purchase_agreement |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW | 65 | 327 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of leases under which lease term was extended | lease |  |  | 5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  |  |  |  |  |  |  | 426,177 | 428,981 | $ 428,981 |  |  |  |  |  |  |
Regulatory liabilities |  |  |  |  |  |  |  |  | $ 651,495 | 653,830 | 653,830 |  |  |  |  |  |  |
PNM | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reserve margin | 20.70% | 17.40% |  |  |  |  |  |  | 0.90% |  |  |  |  |  |  |  |  |
PNM | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reserve margin | 12.50% | 9.80% |  |  |  |  |  |  | 3.40% |  |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  |  |  |  |
Initial payment for relief from obligations |  |  |  |  |  |  |  | $ 15,000 |  |  |  |  |  |  |  |  |  |
PNM | Four Corners | PNM |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Noncontrolling interest, ownership percentage by noncontrolling owners |  |  |  |  |  | 13.00% |  |  |  |  |  |  |  |  |  |  |  |
PNM | COVID-19 | COVID-19 Costs Savings |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory liabilities |  |  |  |  |  |  |  |  | $ 900 | 900 | 900 |  |  |  |  |  |  |
PNM | Deferred COVID-19 Costs | COVID-19 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  |  |  |  |  |  |  | 6,800 | $ 6,900 | $ 6,900 |  |  |  |  |  |  |
PNM | NMPRC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar generation capacity, amount requested for approval to abandon (in megawatts) | MW |  |  | 114 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 | Replacement Resource Portfolio One |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar generation capacity (in megawatts) | MW |  |  | 150 |  |  |  |  |  |  |  |  |  |  | 200 |  |  |  |
Number of megawatts in battery storage facilities (in megawatts) | MW |  |  | 40 |  |  |  |  |  |  |  |  |  |  | 100 |  |  |  |
PNM | Replacement Resource Portfolio One | Subsequent event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar generation capacity (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  | 150 |  |  |  |  |  |
Number of megawatts in battery storage facilities (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  | 40 |  |  |  |  |  |
PNM | Replacement Resource Portfolio Two |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar generation capacity (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  | 100 |  |  |  |
Number of megawatts in battery storage facilities (in megawatts) | MW |  |  | 100 |  |  |  |  |  |  |  |  |  |  | 30 |  |  |  |
PNM | Replacement Resource Portfolio Two | Subsequent event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts in battery storage facilities (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  | 100 |  |  |  |  |  |
PNM | Replacement Resource Portfolio Three |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar generation capacity (in megawatts) | MW |  |  | 300 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts in battery storage facilities (in megawatts) | MW |  |  | 150 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PNM | Replacement Resource Portfolio Three | Subsequent event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar generation capacity (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  | 300 |  |  |  |  |  |
Number of megawatts in battery storage facilities (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  | 150 |  |  |  |  |  |
PNM | Transportation Electrification Program |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expected budgeted expenditures |  |  |  |  |  |  |  |  |  |  |  |  | $ 8,400 |  |  |  |  |
Budget flexibility |  |  |  |  |  |  |  |  |  |  |  |  | 25.00% |  |  |  |  |
Budget portion dedicated to low and moderate income customers |  |  |  |  |  |  |  |  |  |  |  |  | 25.00% |  |  |  |  |
PNM | Portfolio One |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW |  |  |  |  |  |  |  |  |  | 85 | 85 |  |  |  |  |  |  |
PNM | Portfolio Two |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW |  |  |  |  |  |  |  |  |  | 150 | 150 |  |  |  |  |  |  |
PNM | Portfolio Three |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts available in purchase power agreement (in megawatts) | MW |  |  |  |  |  |  |  |  |  | 40 | 40 |  |  |  |  |  |  |
San Juan Generating Station |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Severance costs |  |  |  |  |  |  |  |  | 8,900 |  |  |  |  |  |  |  |  |
Estimated costs of replacement resources |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 8,100 |  |  |
San Juan Generating Station | Other deferred credits |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring reserve |  |  |  |  |  |  |  |  | 36,800 | $ 36,900 | $ 36,900 |  |  |  |  |  |  |
San Juan Generating Station | Employee Severance |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring reserve |  |  |  |  |  |  |  |  | 27,700 |  |  |  |  |  |  |  | $ 9,400 |
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 |  |  |  |  |  |  |  |  |  |  |
San Juan Generating Station | PNM | Other deferred credits |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring reserve |  |  |  |  |  |  |  |  | 35,900 | $ 36,000 | $ 36,000 |  |  |  |  |  |  |
San Juan Generating Station | PNM | Employee Severance |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring reserve |  |  |  |  |  |  |  |  | $ 26,800 |  |  |  |  |  |  |  | 8,100 |
San Juan Generating Station | PNM | Other Restructuring |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring reserve |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8,900 |
San Juan Generating Station | PNM | Economic Development and Workforce Training Costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring reserve |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 19,800 |

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