Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Trading Arrangement: Trading Arrangement [Axis] Maximum Maximum [Member] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Period of time for proposed return to customers the benefit of the reduction in federal corporate income tax rate Public Utilities, Proposed Term to Provide Customers with Benefits Related to Reduction in Federal Corporate Income Tax Rate Public Utilities, Proposed Term To Provide Customers With Benefits Related To Reduction In Federal Corporate Income Tax Rate Short-term Debt, Type [Axis] Short-Term Debt, Type [Axis] Title of 12(b) Security Title of 12(b) Security Subsequent Event Subsequent Event [Member] Carrying Amount Reported Value Measurement [Member] Schedule of Available-for-sale Securities [Table] Debt Securities, Available-for-Sale [Table] First Mortgage Bonds Due 2029 First Mortgage Bonds Due Twenty Twenty Nine [Member] First Mortgage Bonds Due Twenty Twenty Nine Adjustment to Compensation, Amount Adjustment to Compensation Amount Schedule of Available-for-sale Securities, Major Types of Debt and Equity Securities [Axis] Financial Instrument [Axis] Financial Instrument [Axis] Segment Reporting [Abstract] Segment Reporting [Abstract] PNM 2025 Bond At Five Point Seven Five, Due June Twenty Thirty Two PNM April 2025 SUNs At Five Point Seven Five, Due June Twenty Thirty Two [Member] PNM April 2025 SUNs At Five Point Seven Five, Due June Twenty Thirty Two Amounts capitalized Operating Lease, Capitalized Costs Operating Lease, Capitalized Costs Number of nuclear power plants owned Number Of Nuclear Power Plants Owned Number Of Nuclear Power Plants Owned Resource portfolio application, proposed megawatt purchase Public Utilities, Resource Portfolio Application, Proposed Megawatt Purchase Public Utilities, Resource Portfolio Application, Proposed Megawatt Purchase Annual Revenue Collection Public Utilities, Revenue From Proposed Collection Public Utilities, Revenue From Proposed Collection Pension and Other Postretirement Benefit Plans Retirement Benefits [Text Block] Net Earnings Attributable to TXNM per Common Share: Income Loss From Continuing Operations Attributable To Parent Per Share [Abstract] Income Loss From Continuing Operations Attributable To Parent Per Share [Abstract] Loss contingency accrual Loss Contingency Accrual Lease Commitments Lessee, Finance Leases [Text Block] Accounts receivable Contract with Customer, Asset, after Allowance for Credit Loss 2027 Finance Lease, Liability, to be Paid, Year One Derivative Instrument [Axis] Derivative Instrument [Axis] Income tax impact of other OCI changes Other Comprehensive Income (Loss) before Reclassifications, Tax San Juan Generating Station and Four Corners San Juan Generating Station And Four Corners [Member] San Juan Generating Station And Four Corners [Member] Fair Value by Measurement Frequency [Axis] Measurement Frequency [Axis] SRP deferred operating and maintenance costs Public Utilities, Incremental Increase In Revenue Requirement, System Resiliency Plan Deferred Operating And Maintenance Costs Public Utilities, Incremental Increase In Revenue Requirement, System Resiliency Plan Deferred Operating And Maintenance Costs U.S. government US Treasury and Government [Member] Conversion price (in dollars per share) Debt Instrument, Convertible, Conversion Price Consolidated Entities [Axis] Consolidated Entities [Axis] TNMP to PNM TNMP to PNM [Member] TNMP to PNM Other electric operating revenues Revenue Not from Contract with Customer, Other Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Schedule of Regulatory Rate Matters [Domain] Schedule of Regulatory Rate Matters [Domain] Schedule of Regulatory Rate Matters [Domain] Energy production costs Electricity, Generation [Member] Leases [Abstract] Leases [Abstract] Other Comprehensive Income: Other Comprehensive Income (Loss), Net of Tax [Abstract] Consolidated Entities [Domain] Consolidated Entities [Domain] Related Party Transactions Related Party Transactions Disclosure [Text Block] Total financing lease expense Finance Lease, Cost Finance Lease, Cost Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Other (deductions) Other Investment Income (Expense) Other Investment Income (Expense) Catastrophic Event [Domain] Catastrophic Event [Domain] Outstanding at beginning of period (in shares) Outstanding at end of period (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Nuclear Decommissioning Trust Nuclear Decommissioning Trust [Member] Nuclear Decommissioning Trust [Member] Retirement Benefits [Abstract] Retirement Benefits [Abstract] Debt Maturities [Line Items] Debt Maturities [Line Items] Debt Maturities [Line Items] Collateral amount Debt Instrument, Collateral Amount Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Schedule of Assets and Liabilities, Lessee Assets And Liabilities, Lessee [Table Text Block] Assets and Liabilities, Lessee [Table Text Block] Number of reportable segments Number of Reportable Segments Total current liabilities Current liabilities Liabilities, Current Maximum number of shares awarded in year two (in shares) Share-Based Compensation Arrangement By Share-based Payment Award, Maximum Number Of Shares Awarded, In Year Two Share-Based Compensation Arrangement By Share-based Payment Award, Maximum Number Of Shares Awarded, In Year Two Short-term Debt, Type [Domain] Short-Term Debt, Type [Domain] Classification of Mine [Axis] Classification of Mine [Axis] Classification of Mine [Axis] Financing lease cost: Lease, Cost [Abstract] Other current liabilities Finance Lease, Liability, Current, Other Finance Lease, Liability, Current, Other Entity Address, City or Town Entity Address, City or Town Additional community support Public Utilities, Charitable Fund, Amount Public Utilities, Charitable Fund, Amount Requirement to post reclamation bonds Coal Mine Reclamation Bonds To Be Posted With NMMMD Coal Mine Reclamation Bonds To Be Posted With NMMMD Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Title of Individual [Domain] Title and Position [Domain] Annual funding post-term reclamation trust, year one Public Utilities, Annual Funding Post-Term Reclamation Trust, Year One Public Utilities, Annual Funding Post-Term Reclamation Trust, Year One Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Weighted Average Interest Rate Line of Credit Facility, Interest Rate at Period End Projects are estimated to cost Public Utilities, Regulatory Assets Expected Cost Of Projects Public Utilities, Regulatory Assets Expected Cost Of Projects Level 2 Fair Value, Inputs, Level 2 [Member] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Electric Operating Revenues Results of Operations Variable Interest Entity Operating Revenues Results of Operations Variable Interest Entity Operating Revenues Refunds paid under transmission interconnection and security deposit arrangements Repayments From Transmission Interconnection Arrangement And Security Deposit Arrangements Repayments From Transmission Interconnection Arrangement And Security Deposit Arrangements Total Other Comprehensive Income (Loss) Total other comprehensive income (loss) Total other comprehensive income Other Comprehensive Income (Loss), Net of Tax Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Initial forward price (in shares) Settlement shares (in shares) Forward Contract Indexed to Issuer's Equity, Shares Other (deductions) Other Expenses Other deferred charges Other Deferred Costs Net Including Deferred Finance Costs Other Deferred Costs Net Including Deferred Finance Costs Subsequent Event Type [Axis] Subsequent Event Type [Axis] Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Cash collateral under margin arrangements Margin Deposit Assets Financial Statement Location [Domain] Financial Statement Location [Domain] Financial Statement Location [Domain] Schedule of Financial Information by Segment Segment Reporting [Table Text Block] Related Party [Axis] Related and Nonrelated Parties [Axis] Reclamation trust funding, 2027 Reclamation Trust Funding, Year One Reclamation Trust Funding, Year One Repayments of short-term borrowings Repayments of Lines of Credit Equity ratio, percent Public Utilities, Base Rate Review, Recovery, Equity Ratio, Percent Public Utilities, Base Rate Review, Recovery, Equity Ratio, Percent After 1 year through 5 years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Schedule of Future Expected Lease Payments, Operating Lease Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block] Supplemental schedule of noncash investing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Document Period End Date Document Period End Date PNM August 2026 SUNs At Six Point One Two, Due Twenty Thirty Eight PNM August 2026 SUNs At Six Point One Two, Due Twenty Thirty Eight [Member] PNM August 2026 SUNs At Six Point One Two, Due Twenty Thirty Eight Ratio of debt to capital (less than or equal to) Debt Instrument, Covenant, Debt To Capitalization Ratio Debt Instrument, Covenant, Debt To Capitalization Ratio Goodwill fair value exceeded by its carrying value Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount Nuclear fuel, net of accumulated amortization of $29,647 and $27,953 Nuclear fuel, net of accumulated amortization of $29,647 and $27,953 Nuclear Fuel, Net of Amortization Aggregate principal amount Principal Amount Debt Instrument, Face Amount 2028 Lessee, Operating Lease, Liability, to be Paid, Year Two Debt instrument, term Debt Instrument, Term Gross realized (losses) Debt Securities, Available-for-Sale, Realized Loss Net increase in unrealized holding gains arising during the period, income tax (expense) benefit Unrealized holding gains (losses) arising during the period, income tax (expense) benefit OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax Schedule of Interim Distribution Rate Increases Schedule Of Interim Distribution Rate Increases [Table Text Block] Schedule Of Interim Distribution Rate Increases Accumulated depreciation, nuclear fuel Accumulated Amortization Nuclear Fuel Accumulated amortization, nuclear fuel Financing leases Finance Lease, Weighted Average Remaining Lease Term Total fair value of restricted shares that vested Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Accumulated other comprehensive income (loss), net of income taxes Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Shell Company Entity Shell Company Operating lease liabilities Current portion of operating lease liabilities Operating Lease, Liability, Current Net Earnings Per Share of Common Stock: Earnings Per Share, Basic And Diluted, EPS [Abstract] Earnings Per Share, Basic And Diluted, EPS Earnings Per Share Earnings Per Share [Text Block] Four Corners CSA Four Corners CSA [Member] Four Corners CSA [Member] Earnings Per Share [Abstract] Earnings Per Share [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] PNM November 2025 Note Purchase Agreement PNM November 2025 Note Purchase Agreement [Member] PNM November 2025 Note Purchase Agreement Total liabilities Liabilities Pension liability adjustment, income tax expense (benefit) Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax, Attributable to Parent Trading Symbol Trading Symbol Bank Of America, N.A. Bank Of America, N.A. (a) [Member] Bank Of America, N.A. (a) TXNM Revolving Credit Facility TXNM Revolving Credit Facility [Member] TXNM Revolving Credit Facility Request for proposal, new energy resource, megawatts Request For Proposal, New Energy Resource, Megawatts Request For Proposal, New Energy Resource, Megawatts Number of business days to consummate merger after notification Merger Agreement, Business Days To Consummate Merger After Notification Merger Agreement, Business Days To Consummate Merger After Notification Customer related expenses Customer Related Expenses Customer Related Expenses Company Selected Measure Name Company Selected Measure Name Sale of Stock [Domain] Sale of Stock [Domain] Debt offered for prepayment Debt Instrument, Offered For Prepayment Debt Instrument, Offered For Prepayment Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Capital investments Public Utilities, Incremental Increase In Revenue Requirement, Transmission Cost of Service, Capital Investments Public Utilities, Incremental Increase In Revenue Requirement, Transmission Cost of Service, Capital Investments WEB LOC Facility WFB LOC Facility [Member] WFB LOC Facility Credit Facility [Domain] Credit Facility [Domain] Cash Flows From Operating Activities: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Other receivables Other Receivables, Net, Current Dividends declared Dividends Payable, Current Public Utility [Axis] Public Utility [Axis] Bank Of America, N.A. Bank Of America, N.A. (b) [Member] Bank Of America, N.A. (b) Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] 2028 Finance Lease, Liability, to be Paid, Year Two Cancelled common stock previously issued Stock Cancelled During Period, Value Stock Cancelled During Period, Value 2030 Finance Lease, Liability, to be Paid, Year Four Entities [Table] Entities [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Residential Retail Electric, Residential Customers [Member] Retail Electric, Residential Customers Goodwill Goodwill [Text Block] Less: Imputed interest Finance Lease, Liability, Undiscounted Excess Amount PNM July 2025 SUNs At Six Point Zero Three, Due July Twenty Thirty Six PNM July 2025 SUNs At Six Point Zero Three, Due July Twenty Thirty Six [Member] PNM July 2025 SUNs At Six Point Zero Three, Due July Twenty Thirty Six PNM 2026 Term Loan PNM 2026 Term Loan [Member] PNM 2026 Term Loan Operating cash flows from operating leases Operating Lease, Payments Award Timing Predetermined Award Timing Predetermined [Flag] Net utility plant Net property, plant, and equipment Public Utilities, Property, Plant and Equipment, Net Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Level 1 Fair Value, Inputs, Level 1 [Member] Effective tax rate Effective Income Tax Rate Reconciliation, Percent Losses on investment securities Gain (Loss) on Sale of Investments Conversion ratio Debt Instrument, Convertible, Conversion Ratio Solar Wind PPA Solar Wind PPA [Member] Solar Wind PPA Available-for-sale debt securities: Debt Securities, Available-for-Sale [Abstract] Restricted stock (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Regulated Operations [Abstract] Regulated Operations [Abstract] Assets and Liabilities, Lessee [Table] Assets And Liabilities, Lessee [Table] Assets and Liabilities, Lessee [Table] Fair value of long-term debt Long-Term Debt, Fair Value Plan Name [Domain] Plan Name [Domain] Scenario [Domain] Scenario [Domain] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Operating lease right-of-use assets, net of accumulated amortization Operating lease assets, net of amortization Operating Lease, Right-of-Use Asset Accumulated Other Comprehensive Income (Loss) [Roll Forward] AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] PNM 2025 Bond At Six Point One Three, Due June Twenty Thirty Seven PNM April 2025 SUNSs At Six Point One Three, Due June Twenty Thirty Seven [Member] PNM April 2025 SUNSs At Six Point One Three, Due June Twenty Thirty Seven Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Annual payment limitation related to incident Public Utilities, Annual Payment Limitation Related to Incident Public Utilities, Annual Payment Limitation Related to Incident Dividends paid Payments of Ordinary Dividends, Common Stock Expiration Date Trading Arrangement Expiration Date Merger agreement, number of business days to offer prepayment of debt after close of merger Merger Agreement, Number Of Business Days To Offer Prepayment Of Debt After Close Of Merger Merger Agreement, Number Of Business Days To Offer Prepayment Of Debt After Close Of Merger Hedging Relationship [Axis] Hedging Relationship [Axis] Restricted Shares and Performance Based Shares Restricted Stock and Performance Shares [Member] Restricted Stock and Performance Shares [Member] Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Total equity Beginning balance Ending balance Equity, Including Portion Attributable to Noncontrolling Interest Contribution payment period Public Utilities, Donation Contribution, Payment Period Public Utilities, Donation Contribution, Payment Period Wholesale energy sales Wholesale Energy Sales [Member] Wholesale Energy Sales Nonrelated Party Nonrelated Party [Member] Estimate of possible loss Loss Contingency, Estimate of Possible Loss Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Derivative [Table] Derivative [Table] Issuance of common stock Proceeds from Issuance of Common Stock Antidilutive Security, Excluded EPS Calculation [Table] Antidilutive Security, Excluded EPS Calculation [Table] Common stock, no par value (in dollars per share) Common Stock, No Par Value Cash paid for amounts included in the measurement of lease liabilities: Cash Flow, Lessee [Abstract] Cash Flow, Lessee [Abstract] Dispatchable Natural Gas Generation Dispatchable Natural Gas Generation [Member] Dispatchable Natural Gas Generation Cash Flows From Investing Activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Royal Bank of Canada Royal Bank of Canada [Member] Royal Bank of Canada Industrial Retail Electric, Industrial Customers [Member] Retail Electric, Industrial Customers TNMP August 2026 Bond At Five Point Four Six Percent, Due September 1, 2033 TNMP August 2026 Bond At Five Point Four Six Percent, Due September 1, 2033 [Member] TNMP August 2026 Bond At Five Point Four Six Percent, Due September 1, 2033 Unrecognized expense related to stock awards Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Later years Lessee, Operating Lease, Liability, to be Paid, after Year Four Lessee, Operating Lease, Liability, to be Paid, after Year Four Segments [Domain] Segments [Domain] Non-utility property Finance Lease, Right-Of-Use Asset, Gross Finance Lease, Right-Of-Use Asset, Gross Increase in regulatory liabilities Increase (Decrease) in Regulatory Liabilities PNM 2025 Term Loan PNM 2025 Term Loan [Member] PNM 2025 75 Million Term Loan Long-term contract option to purchase, purchase price - percentage of FMV Long Term Contract Option To Purchase, Purchase Price - Percentage Of FMV Long term contract option to purchase, purchase price - percentage of FMV Financing Debt Disclosure [Text Block] Scenario [Axis] Scenario [Axis] UTM regulatory asset Public Utilities, Incremental Increase In Revenue Requirement, Distribution Cost Recovery Factor, Unified Tracker Mechanism Deferred Revenue, Regulatory Asset Public Utilities, Incremental Increase In Revenue Requirement, Distribution Cost Recovery Factor, Unified Tracker Mechanism Deferred Revenue, Regulatory Asset Net plant in service and plant held for future use Public Utilities Property Plant And Equipment In Service, Net Public Utilities Property Plant And Equipment In Service, Net Business Combination [Table] Business Combination [Table] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract] Sales and use tax refund Sales And Use Tax Refund, Claim Sales And Use Tax Refund, Claim Available-for-Sale Debt Securities, Available-for-Sale, Fair Value, Fiscal Year Maturity [Abstract] Right-of-way lease payments Lessee, Right-Of-Way Lease, Payments Right-Of-Way Lease Payments Financing leases Finance Lease, Weighted Average Discount Rate, Percent Stated interest rate Interest Rate Debt Instrument, Interest Rate, Stated Percentage Dividends declared on common stock Dividends declared on common stock Dividends, Common Stock, Cash Total common stockholder’s equity Beginning balance Ending balance Equity, Attributable to Parent Annual funding post-term reclamation trust, remainder of year Public Utilities, Annual Funding Post-Term Reclamation Trust, Remainder Of Year Public Utilities, Annual Funding Post-Term Reclamation Trust, Remainder Of Year ASSETS Assets [Abstract] Other investments Other Investments Maximum annual premium per incident Public Utilities, Maximum Annual Premium Per Incident Public Utilities, Maximum Annual Premium Per Incident Lessee, operating lease, unguaranteed residual value Lessee, Operating Lease, Unguaranteed Residual Value Lessee, Operating Lease, Unguaranteed Residual Value Derivative agreements Derivative, Number of Agreements Entered Derivative, Number of Agreements Entered Insider Trading Policies and Procedures [Line Items] Allowance for uncollectible accounts Accounts Receivable, Allowance for Credit Loss, Current Performance Shares Performance Shares [Member] Prepaid and other current assets Prepaid Expense and Other Assets, Current Deferred income tax expense Deferred income tax expense Deferred Income Tax Expense (Benefit) Schedule of Incremental Increase in Revenue Requirement Schedule Of Incremental Increase In Revenue Requirement [Table Text Block] Schedule Of Incremental Increase In Revenue Requirement Regulatory assets Regulatory Asset, Current Related Party Transaction, by Transaction Type [Domain] Related Party Transaction, by Transaction Type [Domain] Related Party Transaction, by Transaction Type [Domain] Indentures governing the remaining outstanding Long-Term Debt, Net Long-Term Debt, Net Surface Surface [Member] Surface [Member] Number of shares vested at one-time sign-on (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Granted and Vested, During Period Share-based Compensation Arrangement by Share-based Payment Award, Granted and Vested, During Period Number of operating segments Number of Operating Segments Entity Central Index Key Entity Central Index Key Revenues Recorded Public Utilities, Revenue From Renewable Energy Rider Public Utilities, Revenue From Renewable Energy Rider Equity: Equity [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Other OCI changes (pre-tax) Other Comprehensive Income (Loss), before Reclassifications, Net of Tax TNMP to TXNM TNMP To TXNM [Member] TNMP to TXNM [Member] Insurance Carrier [Domain] Insurance Carrier [Domain] Insurance Carrier [Domain] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Dividends declared on preferred stock Dividends, Preferred Stock, Cash Designated as Hedging Instrument Designated as Hedging Instrument [Member] Annual lease payments Lessee, Right-Of-Way Lease, Annual Payments Annual lease payments Maximum potential assessment per incident Public Utilities, Maximum Potential Assessment Per Incident Public Utilities, Maximum Potential Assessment Per Incident Schedule of Regulatory Rate Matters [Axis] Schedule of Regulatory Rate Matters [Axis] Schedule of Regulatory Rate Matters [Axis] Unrealized Gains Debt Securities, Available-for-Sale, Unrealized Gain Total minimum lease payments Finance Lease, Liability, to be Paid Restricted stock Restricted Stock Restricted Stock [Member] AOCI Total AOCI Attributable to Parent [Member] Leases, Operating [Table] Leases, Operating [Table] Leases, Operating [Table] All Individuals All Individuals [Member] Short-Term Lease Type [Domain] Short-Term Lease Type [Domain] Short-Term Lease Type [Domain] Number of mortgage bonds Number Of Mortgage Bonds Number Of Mortgage Bonds Executive Management [Member] Loss on long-term purchase commitment Loss on Long-Term Purchase Commitment [Member] Energy efficiency cost recovery factor, performance bonus Energy Efficiency Cost Recovery Factor, Performance Bonus Energy Efficiency Cost Recovery Factor, Performance Bonus Period of time stock expense is expected to be recognized Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Financial Position Variable Interest Entity, Statement Of Financial Position [Abstract] Variable Interest Entity, Statement Of Financial Position Purchased through May 2028 Purchased Through May 30, 2028 [Member] Purchased Through May 30, 2028 [Member] Lease to be executed, term of contract Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract Statement [Line Items] Statement [Line Items] Total assets Total Assets Assets Operating Lessee, Operating Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan [Table] Deferred Credits and Other Liabilities: Other Liabilities, Noncurrent [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract] Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract] Net gains from equity securities sold Equity Securities, FV-NI, Realized Gain (Loss) Reclassification adjustment for amortization of experience losses recognized as net periodic benefit cost, net of income tax (benefit) of $(16), $(349), $(383), and $(1,047) Reclassification adjustment for amortization of experience losses recognized as net periodic benefit cost, net of income tax (benefit) of $(16), $(349), $(383), and $(1,047) Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax Convertible Debt Convertible Debt [Member] Interest charges Interest Expense, Nonoperating Stock-Based Compensation Share-Based Payment Arrangement [Text Block] Market-Based Shares Market-Based Shares [Member] Market-Based Shares [Member] Contract assets Commodity Contract Asset, Current PEO PEO [Member] Defined benefit plan, assumptions used calculating benefit obligation related to anticipated contributions, weighted average discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation Related To Anticipated Contributions, Weighted Average Discount Rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation Related To Anticipated Contributions, Weighted Average Discount Rate MUFG Securities EMEA plc MUFG Securities EMEA plc (b) [Member] MUFG Securities EMEA plc (b) TXNM ATM Programs (in shares) Incremental Common Shares Attributable to Dilutive Effect of Equity Forward Agreements Schedule of Renewable Energy Rider Schedule Of Renewable Energy Rider [Table Text Block] Schedule Of Renewable Energy Rider Goodwill Goodwill Retirement Plan Type [Axis] Retirement Plan Type [Axis] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Long-term contract option to purchase, ownership percentage (up to) Long Term Contract Option To Purchase, Ownership Percentage Long term contract option to purchase, ownership percentage Total net gains (losses) on equity securities Equity Securities, FV-NI, Gain (Loss) Reclamation trust funding, 2026 Reclamation Trust Funding, Remainder Of The Year Reclamation Trust Funding, Remainder Of The Year Retained Earnings Retained Earnings [Member] Operating lease liabilities Long-term portion of operating lease liabilities Operating Lease, Liability, Noncurrent Revolving Credit Facility Revolving Credit Facility [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Award Timing Disclosures [Line Items] Schedule of Carrying Amount and Fair Value of Items Not Recorded at Fair Value Fair Value, by Balance Sheet Grouping [Table Text Block] Diluted (in dollars per share) Earnings Per Share, Diluted Merger agreement period extension Business Combination, Merger Agreement Period Extension Business Combination, Merger Agreement Period Extension Unrealized Gains Unrealized Gain (Loss) on Investments Proceeds from long-term lines of credit Proceeds from Long-Term Lines of Credit Public utilities budget dedication to low income customers Public Utilities, Budget Dedication To Low-Income Customers Public Utilities, Budget Dedication To Low-Income Customers Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Total revenues from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Income tax impact of amounts reclassified Reclassification from AOCI, Current Period, Tax Program costs related to energy efficiency, in year two Public Utilities, Program Costs Related To Energy Efficiency, Year Two Public Utilities, Program Costs Related To Energy Efficiency, Year Two Equity contribution from parent Adjustments To Additional Paid In Capital, Parent Contributions Adjustments To Additional Paid In Capital, Parent Contributions TXNM to TNMP TXNM To TNMP [Member] TXNM to Tnmp [Member] TXNM common stockholders’ equity: PNM common stockholder’s equity: Common Stockholder’s Equity: Company Common Stockholders Equity Company Common Stockholders Equity Awards of common stock Stock Repurchased During Period, Value Other Deferred Credits Other Deferred Credits [Member] Other Deferred Credits [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Interest billings: Interest Charges [Member] Interest Charges [Member] Number of sites Public Utilities, Number Of Sites Number Of Sites Depreciation and amortization Cost, Depreciation and Amortization Other current liabilities Increase (Decrease) in Other Current Liabilities Public utilities dedication to low income customers percent Public Utilities, Dedication To Low-Income Customers, Percent Public Utilities, Dedication To Low-Income Customers, Percent Grid modernization, maintenance cost Public Utilities, Grid Modernization, Decrease In Operations And Maintenance Cost, Percent Public Utilities, Grid Modernization, Decrease In Operations And Maintenance Cost, Percent TNMP August 2026 Bond Purchase Agreement TNMP August 2026 Bond Purchase Agreement [Member] TNMP August 2026 Bond Purchase Agreement Surety bond Loss Contingency, Surety Bond Loss Contingency, Surety Bond PNM August 2026 Note Purchase Agreement PNM August 2026 Note Purchase Agreement [Member] PNM August 2026 Note Purchase Agreement Sale of Stock [Axis] Sale of Stock [Axis] Title of Individual [Axis] Title and Position [Axis] PNM August 2026 SUNs At Five Point Forty Four, Due Twenty Twenty Nine PNM August 2026 SUNs At Five Point Forty Four, Due Twenty Twenty Nine [Member] PNM August 2026 SUNs At Five Point Forty Four, Due Twenty Twenty Nine Other Income and Deductions: Other Nonoperating Income (Expense) [Abstract] Total operating expenses Operating Income (Loss) Real estate funds Other Real Estate RFP Request, Period Two RFP Request, Period Two [Member] RFP Request, Period Two Merger agreement, number of business days to offer prepayment of debt Merger Agreement, Number Of Business Days To Offer Prepayment Of Debt Merger Agreement, Number Of Business Days To Offer Prepayment Of Debt Schedule of Future Expected Lease Payments, Finance Lease Finance Lease, Liability, to be Paid, Maturity [Table Text Block] Remainder of 2026 Finance Lease, Liability, to be Paid, Remainder of Fiscal Year Public Utilities, Commitments And Contingencies [Line Items] Public Utilities, Commitments And Contingencies [Line Items] Public Utilities, Commitments And Contingencies [Line Items] Cumulative Preferred Stock of Subsidiary without mandatory redemption requirements ($100 stated value; 10,000,000 shares authorized; issued and outstanding 115,293 shares) Cumulative Preferred Stock without mandatory redemption requirements ($100 stated value; 10,000,000 shares authorized; issued and outstanding 115,293 shares) Cumulative Preferred Stock Of Subsidiary Without Mandatory Redemption Requirements Cumulative Preferred Stock Of Subsidiary Without Mandatory Redemption Requirements Fair Value Adjustment for Cash Flow Hedges: Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract] Merger Business Combination [Text Block] Financing leases: Finance Lease, Assets And Liabilities, Lessee [Abstract] Finance Lease, Assets and Liabilities, Lessee [Abstract] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Service cost Defined Benefit Plan, Service Cost Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Common stock, shares issued (in shares) Common Stock, Shares, Issued Entity Information [Line Items] Entity Information [Line Items] The Bank of Nova Scotia The Bank of Nova Scotia [Member] The Bank of Nova Scotia Variable Interest Entities [Abstract] Variable Interest Entities [Abstract] Variable Interest Entities [Abstract] Product and Service [Domain] Product and Service [Domain] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Accumulated deferred income taxes Deferred Income Tax Liabilities, Net Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] 2029 Lessee, Operating Lease, Liability, to be Paid, Year Three Termination Date Trading Arrangement Termination Date Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value, Recurring and Nonrecurring [Table] Derivative, loss on derivative Derivative, Loss on Derivative Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Other current liabilities Other Liabilities, Current Investment securities Investment securities Marketable Securities Fair Value as of Grant Date Award Grant Date Fair Value Fuel burn Electricity, Fuel Burn [Member] Electricity, Fuel Burn Estimated cost of the project is expected to be reviewed in a future rate Public Utilities, Estimated Cost Of The Project Is Expected In Future Rate Sites Public Utilities, Estimated Cost Of The Project Is Expected In Future Rate Sites Redemption price (as a percent) Debt Instrument, Redemption Price, Percentage Schedule of Goodwill [Table] Goodwill [Table] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Battery Storage ESA Battery Storage ESA [Member] Battery Storage ESA Arrangement Duration Trading Arrangement Duration Number of monitoring wells containing free-phase hydrocarbon products Number Of Monitoring Wells Containing Free-Phase Hydrocarbon Products Number Of Monitoring Wells Containing Free-Phase Hydrocarbon Products Solar PPA Solar PPA [Member] Solar PPA Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Economic development fund Public Utilities, Economic Development Fund, Amount Public Utilities, Economic Development Fund, Amount Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures 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[Member] Commercial Providers [Member] Jointly Owned Utility Plant [Domain] Jointly Owned Utility Plant [Domain] Financial Statement Location [Axis] Financial Statement Location [Axis] Financial Statement Location [Axis] Adjustment to Compensation: Adjustment to Compensation [Axis] Amounts reclassified from AOCI (pre-tax) Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Treasury lock agreements had an average fixed rate Derivative, Average Fixed Interest Rate Dividends Payable [Line Items] Dividends Payable [Line Items] Dividends Payable [Table] Dividends Payable [Table] Liability insurance coverage Public Utilities, Liability Insurance Coverage Public Utilities, Liability Insurance Coverage Annual funding post-term reclamation trust Public Utilities, Annual Funding Post-Term Reclamation Trust Public Utilities, Annual Funding Post-Term Reclamation Trust Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate 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(c) [Member] Bank Of America, N.A. (c) Asset retirement obligations Asset Retirement Obligations, Noncurrent Realizing a pre-tax net loss Loss on Derivative Instruments, Pretax Number of extensions Debt Instrument, Number Of Extensions Debt Instrument, Number Of Extensions Equity Components [Axis] Equity Components [Axis] Equity Components [Axis] Related Party Related Party [Member] Income taxes paid, net Income taxes paid, net Income Tax Paid, after Refund Received Annual Increase in Revenue Public Utilities, Actual Annual Increase Annual Distribution Revenue Requirement Public Utilities, Actual Annual Increase Annual Distribution Revenue Requirement Entity Interactive Data Current Entity Interactive Data Current (Earnings) Attributable to Valencia Non-controlling Interest Valencia non-controlling interest Earnings attributable to non-controlling interest Net Income (Loss) Attributable to Noncontrolling Interest Purchase of common stock Public Utilities, Purchase Of Common Stock, Amount Public Utilities, Purchase Of Common Stock, Amount Regulatory disallowances Regulatory Disallowance Regulatory Disallowance Equity contribution from parent Proceeds from Contributions from Parent Reclassification adjustment for (gains) included in net earnings, net of income tax expense of $28, $69, $93, and $155 Reclassification adjustment for (gains) included in net earnings, net of income tax expense of $28, $69, $93, and $155 Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Entity Small Business Entity Small Business Administrative and general - corporate allocation General And Administrative Expense, Corporate General And Administrative Expense, Corporate Plant in service and plant held for future use Plant in service and plant held for future use Public Utilities, Property, Plant and Equipment, Plant in Service Restricted Cash included in Other Current Assets and Other Deferred Charges on Condensed Consolidated Balance Sheets: Restricted Cash [Abstract] Comprehensive Income Attributable to TXNM Comprehensive Income (Loss), Net of Tax, Attributable to Parent NMPRC approved credit facility Debt Instruments, NMPRC Approved Credit Facility Debt Instruments, NMPRC Approved Credit Facility System Resiliency Plan System Resiliency Plan [Member] System Resiliency Plan Treasury Lock Agreements Treasury Lock Agreements [Member] Treasury Lock Agreements Accounts receivable and unbilled revenues Increase Decrease In Accounts Receivable And Unbilled Revenues The net change during the period in the amount due from customers for the credit sale of goods and services; includes accounts receivable billed and unbilled. Utility Plant [Domain] Utility Plant [Domain] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] 2029 Finance Lease, Liability, to be Paid, Year Three Document Type Document Type Repurchased face amount Debt Instrument, Repurchased Face Amount Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] PNM to TNMP PNM To TNMP [Member] Pnm to Tnmp [Member] Purchase Commitment, Excluding Long-term Commitment [Domain] Purchase Commitment, Excluding Long-Term Commitment [Domain] Jointly-Owned Generating Facilities [Axis] Jointly-Owned Generating Facilities [Axis] Jointly-Owned Generating Facilities [Axis] Significant Accounting Policies and Responsibility for Financial Statements Significant Accounting Policies [Text Block] Cash and cash equivalents Cash and Cash Equivalents [Member] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Grid modernization, initial term Public Utilities, Grid Modernization, Initial Term Public Utilities, Grid Modernization, Initial Term Long-term borrowings Proceeds from Issuance of Long-Term Debt Local Phone Number Local Phone Number OPEB Plan Other Postretirement Benefits Plan [Member] TXNM 2026 Delayed-Draw Term Loan TXNM 2026 Delayed-Draw Term Loan [Member] TXNM 2026 Delayed-Draw Term Loan Commitments and Contingencies Related to the Environment And Other [Domain] Commitments and Contingencies Related to the Environment And Other, Nature [Domain] Commitments and Contingencies Related to the Environment And Other, Nature Earnings before Income Taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Number of megawatts purchased (in megawatts) Number Of Mega Watts Purchased Number Of Mega Watts Purchased Commitments and Contingencies (Note 11) Commitments and Contingencies Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Valencia’s transactions with its owner Proceeds (Payments) Of Ordinary Dividends, Noncontrolling Interest Proceeds (Payments) Of Ordinary Dividends, Noncontrolling Interest Unrealized Gains on Available-for-Sale Debt Securities: OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax [Abstract] Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Income Tax Contingency [Table] Income Tax Contingency [Table] Preferred Stock Dividend Requirements of Subsidiary Subsidiary preferred stock dividends Preferred Stock Dividend Requirements of Subsidiary Preferred stock cash dividend declared by a subsidiary of the entity during the period. This element includes paid and unpaid dividends declared during the period. Executive Category: Executive Category [Axis] Counterparty Name [Axis] Counterparty Name [Axis] LIABILITIES AND STOCKHOLDER’S EQUITY Liabilities and Equity [Abstract] Operating lease, residual value of leased asset Operating Lease, Residual Value of Leased Asset Materials, supplies, and fuel stock Materials and supplies Inventory, Net Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount San Juan Generating Station San Juan Generating Station [Member] San Juan Generating Station [Member] Schedule of Variable Interest Entities [Table] Variable Interest Entity [Table] Supplemental Cash Flow Disclosures: Supplemental Cash Flow Information [Abstract] Reclassification adjustment for amortization of losses recognized in net earnings, net of income tax (expense) benefit of $(12), $0, $(36), and $0 Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax PEO Name PEO Name Pollution Control Revenue Bonds Pollution Control Revenue Bonds [Member] Pollution Control Revenue Bonds Fair Value Adjustment for Cash Flow Hedges Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Property, Plant and Equipment, Type [Axis] Long-Lived Asset, Class [Axis] Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Entity Tax Identification Number Entity Tax Identification Number Purchases for resale Electricity, Purchased [Member] Change in fair market value, net of income tax (expense) benefit of $0, $(242), $0, and $391 Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Net Earnings Results Of Operations Variable Interest Entity Other (Income) Expense Results Of Operations Variable Interest Entity Other (Income) Expense Subsidiary preferred stock dividends Preferred Stock Dividends, Income Statement Impact Hedge funds Other Multi-Strategy Fund Other Multi-Strategy Fund Accounts payable Increase (Decrease) in Accounts Payable Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Maximum amount under nuclear electric insurance limited Public Utilities, Maximum Amount under Nuclear Electric Insurance Limited Public Utilities, Maximum Amount under Nuclear Electric Insurance Limited TNMP 2025 Bond At 4.83%, Due July 31, 2030 TNMP 2025 Bond At 4.83%, Due July 31, 2030 [Member] TNMP 2025 Bond At 4.83%, Due July 31, 2030 Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Contribution to fund Public Utilities, Donation Contribution, Amount Public Utilities, Donation Contribution, Amount TXNM TXNM [Member] TXNM Comprehensive Income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Measurement Frequency [Domain] Measurement Frequency [Domain] Debt Instrument [Axis] Debt Instrument [Axis] Stock based compensation expense Share-Based Payment Arrangement, Noncash Expense Taxes other than income taxes Utilities Operating Expense, Taxes Total lease expense for the period Lease, Cost Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Axis] Return of dividends previously paid (Note 12) Return Of Dividends Previously Paid Return Of Dividends Previously Paid Maximum number of shares awarded, remainder of year (in shares) Share-Based Compensation Arrangement By Share-based Payment Award, Number Of Shares Excluded, Remainder Of Year Share-Based Compensation Arrangement By Share-based Payment Award, Number Of Shares Excluded, Remainder Of Year Amount of related party transaction Related Party Transaction, Amounts of Transaction Basic (in dollars per share) Earnings Per Share, Basic Total current assets Current assets Assets, Current Insider Trading Arrangements [Line Items] Cumulative preferred stock of subsidiary, shares issued (in shares) Cumulative Preferred Stock Of Subsidiary Without Mandatory Redemption Requirements Shares Issued Cumulative Preferred Stock Of Subsidiary Without Mandatory Redemption Requirements Shares Issued Long-term Debt, net of Unamortized Premiums, Discounts, and Debt Issuance Costs (includes $316,892 and $324,531 related to ETBC I) Long-term debt, net of unamortized premiums, discounts, and debt issuance costs Long-term Debt Long-Term Debt, Excluding Current Maturities Short-term lease expense Short-Term Lease, Cost Requested recovery rate Public Utilities, Base Rate Recovery Public Utilities, Base Rate Recovery Accounts receivable, net of allowance for credit losses of $1,616 and $1,394 Accounts receivable, net of allowance for credit losses of $1,616 and $1,394 Accounts receivable Accounts Receivable, after Allowance for Credit Loss, Current Schedule of Short-term Debt Schedule of Short-Term Debt [Table Text Block] Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Tax benefits on merger-related costs Effective Income Tax Rate Reconciliation Tax Expense Benefit Merger Related Costs Amount Effective Income Tax Rate Reconciliation Tax Expense Benefit Merger Related Costs Amount Expected volatility Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate Fair Value Measurement [Domain] Fair Value Measurement [Domain] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Cover page. Cover [Abstract] TXNM ATM Programs TXNM ATM Program [Member] TXNM ATM Program Cumulative preferred stock of subsidiary, stated value (in dollars per share) Cumulative Preferred Stock Of Subsidiary Without Mandatory Redemption Requirements Par Or Stated Value Per Share Cumulative Preferred Stock Of Subsidiary Without Mandatory Redemption Requirements Par Or Stated Value Per Share Schedule of Rate Increases for Transmission Costs Schedule Of Rate Increases For Transmission Costs [Table Text Block] Schedule of Rate Increases for Transmission Costs [Table Text Block] Equity Awards Adjustments Equity Awards Adjustments [Member] Distribution agreement Sale Of Stock, Distribution Agreement, Aggregate Value Sale Of Stock, Distribution Agreement, Aggregate Value Hedging Relationship [Domain] Hedging Relationship [Domain] Lease to be executed, fixed consideration Lessee, Operating Lease, Lease Not Yet Commenced, Fixed Consideration Lessee, Operating Lease, Lease Not Yet Commenced, Fixed Consideration TNMP Merger Backstop Term Loan TNMP Merger Backstop Term Loan [Member] TNMP Merger Backstop Term Loan Cost of energy Electric operating revenues Electricity [Member] Bonds Notes Payable, Other Payables [Member] Investment owned, net assets, percentage Investment Owned, Net Assets, Percentage Plan Name [Axis] Plan Name [Axis] Nuclear plant Nuclear Plant [Member] PNM Revolving Credit Facility PNM Revolving Credit Facility [Member] PNM Revolving Credit Facility Other liabilities Increase (Decrease) in Other Noncurrent Liabilities Net other income and deductions Other Nonoperating Income (Expense) Customer reclamation funding cost Customer Reclamation Funding Cost, Maximum Customer Reclamation Funding Cost, Maximum Corporate and other Other Debt Obligations [Member] Total TXNM Common Stockholders’ Equity Total PNM Common Stockholder’s Equity Parent [Member] Amounts capitalized Finance Lease, Capitalized Costs Finance Lease, Capitalized Costs Rate credits Public Utilities, Annual Rate Credits Public Utilities, Annual Rate Credits Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Administrative and general General and Administrative Expense Financial contributions to help train and build new workforce and fund economic development projects in local communities Public Utilities, Financial Contributions Related To Training And Economic Development Public Utilities, Financial Contributions Related To Training And Economic Development Schedule of Gross Realized Gains and Losses Schedule of Realized Gain (Loss) [Table Text Block] Fair Value of Derivative and Other Financial Instruments Derivatives and Fair Value [Text Block] ETBC 1 Senior Secured Energy Transition Bonds, Series A [Member] Senior Secured Energy Transition Bonds, Series A Hedging Designation [Domain] Hedging Designation [Domain] Energy Storage Facilities Energy Storage Facilities [Member] Energy 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[Abstract] Right-Of-Use Asset Obtained In Exchange For Lease Liability [Abstract] Accounts payable Payable Accounts Payable, Current Interconnection withdrawal penalty billings Interconnection Withdrawal Penalty Billings Interconnection Withdrawal Penalty Billings Other, net Other Noncash Income (Expense) Payment defaults under agreements Collaborative Arrangement, Owner Obligations, Default, Amount Collaborative Arrangement, Owner Obligations, Default, Amount Cash used to support bank letter or credit arrangement Cash Used To Support Bank Letter Or Credit Arrangement Cash used to support bank letter or credit arrangement Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Mine Reclamation Trust Mine Reclamation Trust [Member] Mine Reclamation Trust [Member] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Entity Filer Category Entity Filer Category Interest rate Debt Instrument, Interest Rate During Period Related Party Transaction, By Transaction Type [Axis] Related Party Transaction, By Transaction Type [Axis] Related Party Transaction, By Transaction Type [Axis] Financing Finance Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract] Payment for fixed costs Long Term Contract For Purchase of Electric Power Fixed Costs Long Term Contract For Purchase of Electric Power Fixed Charges Grid modernization investment Public Utilities, Grid Modernization Investment Public Utilities, Grid Modernization Investment Net Earnings Net earnings Net earnings before subsidiary preferred stock dividends Net earnings Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Right-of-use asset and operating lease lability, retirement Operating Lease, Right-Of-Use Asset And Operating Lease Liability Retirement Operating Lease, Right-Of-Use Asset And Operating Lease Liability Retirement Current Assets: Assets, Current [Abstract] Number of debt issuances Debt Instrument, Number Of Debt Issuances Debt Instrument, Number Of Debt Issuances Regulatory and Rate Matters Regulatory And Rate Matters [Text Block] Regulatory And Rate Matters [Text Block] Entity Address, Address Line One Entity Address, Address Line One Operating leases additions Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Released (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Valencia County Valencia County [Member] Valencia County Cancelled common stock previously issued Payment For Cancellation Of Common Stock Previously Issued Payment For Cancellation Of Common Stock Previously Issued Income Taxes Income taxes (benefit) Income Tax Expense (Benefit) Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Principles of Consolidation Consolidation, Policy [Policy Text Block] Non-employee Members of the Board of Directors Non-employee Members of the Board of Directors [Member] Non-employee Members of the Board of Directors Valencia Variable Interest Entity, Primary Beneficiary [Member] TNMP 2025 Bond At 5.12%, Due July 31, 2032 TNMP 2025 Bond At 5.12%, Due July 31, 2032 [Member] TNMP 2025 Bond At 5.12%, Due July 31, 2032 Statement [Table] Statement [Table] Catastrophic Event [Axis] Catastrophic Event [Axis] Public authority Retail Electric, Public Authority Customers [Member] Retail Electric, Public Authority Customers Regulatory liabilities Regulatory liabilities - Current Regulatory Liability, Current Transmission interconnection and security deposit arrangements Proceeds From Transmission Interconnection And Security Deposit Arrangements Proceeds From Transmission Interconnection And Security Deposit Arrangements Derivative, term of contract Derivative, Contract Term Interest income Investment Income, Interest Conversion notices and settlements Debt Conversion, Converted Instrument, Amount TNMP August 2026 Bond At Five Point Two Three Percent, Due September 1, 2031 TNMP August 2026 Bond At Five Point Two Three Percent, Due September 1, 2031 [Member] TNMP August 2026 Bond At Five Point Two Three Percent, Due September 1, 2031 Total deferred credits and other liabilities Liabilities, Other than Long-Term Debt, Noncurrent Estimated project costs Estimated Project Costs Estimated Project Costs TXNM 2026 ATM Program TXNM 2026 ATM Program [Member] TXNM 2026 ATM Program Short-term borrowings Short-term borrowings Proceeds from Short-Term Debt Renewable Energy Rider Renewable Energy Rider [Member] Renewable Energy Rider [Member] Non-lease component, percent of lease liability Non-Lease Component, Percent Of Lease Liability Non-Lease Component, Percent Of Lease Liability Assets and Liabilities, Lessee [Line Items] Assets And Liabilities, Lessee [Line Items] [Line Items] for Assets and Liabilities, Lessee [Table] TCOS Public Utilities, Incremental Increase In Revenue Requirement, Transmission Cost of Service Public Utilities, Incremental Increase In Revenue Requirement, Transmission Cost of Service