<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Version>2.4.1.9</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>1187</ContextCount>
  <ElementCount>794</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>271</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>22</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information Document</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/DocumentAndEntityInformationDocument</Role>
      <ShortName>Document and Entity Information Document</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Consolidated Statements of Earnings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ConsolidatedStatementsOfEarnings</Role>
      <ShortName>Consolidated Statements of Earnings</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002000 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002501 - Statement - Consolidated Statements of Comprehensive Income (Loss) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ConsolidatedStatementsOfComprehensiveIncomeLossParenthetical</Role>
      <ShortName>Consolidated Statements of Comprehensive Income (Loss) (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1004000 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1004501 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1005000 - Statement - Consolidated Statements of Changes in Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ConsolidatedStatementsOfChangesInEquity</Role>
      <ShortName>Consolidated Statements of Changes in Equity</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Summary of the Business and Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SummaryOfBusinessAndSignificantAccountingPolicies</Role>
      <ShortName>Summary of the Business and Significant Accounting Policies</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SegmentInformation</Role>
      <ShortName>Segment Information</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Sale of First Choice</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SaleOfFirstChoice</Role>
      <ShortName>Sale of First Choice</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Regulatory Assets and Liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/RegulatoryAssetsAndLiabilities</Role>
      <ShortName>Regulatory Assets and Liabilities</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/StockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Financing</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/Financing</Role>
      <ShortName>Financing</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Lease Commitments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/LeaseCommitments</Role>
      <ShortName>Lease Commitments</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Fair Value of Derivative and Other Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FairValueOfDerivativeAndOtherFinancialInstruments</Role>
      <ShortName>Fair Value of Derivative and Other Financial Instruments</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Variable Interest Entities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/VariableInterestEntities</Role>
      <ShortName>Variable Interest Entities</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - Earnings and Dividends Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/EarningsAndDividendsPerShare</Role>
      <ShortName>Earnings and Dividends Per Share</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - Pension and Other Postretirement Benefits</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/PensionAndOtherPostretirementBenefits</Role>
      <ShortName>Pension and Other Postretirement Benefits</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - Stock-Based Compensation Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/StockBasedCompensationPlans</Role>
      <ShortName>Stock-Based Compensation Plans</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2116100 - Disclosure - Construction Program and Jointly-Owned Electric Generating Plants</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ConstructionProgramAndJointlyOwnedElectricGeneratingPlants</Role>
      <ShortName>Construction Program and Jointly-Owned Electric Generating Plants</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2117100 - Disclosure - Asset Retirement Obligations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/AssetRetirementObligations</Role>
      <ShortName>Asset Retirement Obligations</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2118100 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/CommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2119100 - Disclosure - Regulatory and Rate Matters</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/RegulatoryAndRateMatters</Role>
      <ShortName>Regulatory and Rate Matters</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2120100 - Disclosure - Related Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/RelatedPartyTransactions</Role>
      <ShortName>Related Party Transactions</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2122100 - Disclosure - Accumulated Other Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/AccumulatedOtherComprehensiveIncomeLoss</Role>
      <ShortName>Accumulated Other Comprehensive Income (Loss)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2126100 - Disclosure - Goodwill; Impairments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/GoodwillImpairments</Role>
      <ShortName>Goodwill; Impairments</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2127100 - Disclosure - Quarterly Operating Results (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/QuarterlyOperatingResultsUnaudited</Role>
      <ShortName>Quarterly Operating Results (Unaudited)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2128100 - Schedule - Schedule I - Condensed Financial Information of Parent Company</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ScheduleICondensedFinancialInformationOfParentCompany</Role>
      <ShortName>Schedule I - Condensed Financial Information of Parent Company</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2129100 - Schedule - Schedule II - Valuation and Qualifying Accounts</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ScheduleIiValuationAndQualifyingAccounts</Role>
      <ShortName>Schedule II - Valuation and Qualifying Accounts</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Summary of the Business and Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SummaryOfBusinessAndSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of the Business and Significant Accounting Policies (Policies)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2301302 - Disclosure - Summary of the Business and Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SummaryOfBusinessAndSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary of the Business and Significant Accounting Policies (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2302301 - Disclosure - Segment Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SegmentInformationTables</Role>
      <ShortName>Segment Information (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Regulatory Assets and Liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/RegulatoryAssetsAndLiabilitiesTables</Role>
      <ShortName>Regulatory Assets and Liabilities (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - Financing (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FinancingTables</Role>
      <ShortName>Financing (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - Lease Commitments Lease Commitments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/LeaseCommitmentsLeaseCommitmentsTables</Role>
      <ShortName>Lease Commitments Lease Commitments (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - Fair Value of Derivative and Other Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FairValueOfDerivativeAndOtherFinancialInstrumentsTables</Role>
      <ShortName>Fair Value of Derivative and Other Financial Instruments (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Variable Interest Entities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/VariableInterestEntitiesTables</Role>
      <ShortName>Variable Interest Entities (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2312301 - Disclosure - Earnings and Dividends Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/EarningsAndDividendsPerShareTables</Role>
      <ShortName>Earnings and Dividends Per Share (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/IncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2314301 - Disclosure - Pension and Other Postretirement Benefits (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/PensionAndOtherPostretirementBenefitsTables</Role>
      <ShortName>Pension and Other Postretirement Benefits (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2315301 - Disclosure - Stock-Based Compensation Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/StockBasedCompensationPlansTables</Role>
      <ShortName>Stock-Based Compensation Plans (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2316301 - Disclosure - Construction Program and Jointly-Owned Electric Generating Plants Schedule of Jointly Owned Utility Plants (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ConstructionProgramAndJointlyOwnedElectricGeneratingPlantsScheduleOfJointlyOwnedUtilityPlantsTables</Role>
      <ShortName>Construction Program and Jointly-Owned Electric Generating Plants Schedule of Jointly Owned Utility Plants (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2317301 - Disclosure - Asset Retirement Obligations (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/AssetRetirementObligationsTables</Role>
      <ShortName>Asset Retirement Obligations (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2320301 - Disclosure - Related Party Transactions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/RelatedPartyTransactionsTables</Role>
      <ShortName>Related Party Transactions (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2322301 - Disclosure - Accumulated Other Comprehensive Income (Loss) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/AccumulatedOtherComprehensiveIncomeLossTables</Role>
      <ShortName>Accumulated Other Comprehensive Income (Loss) (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2327301 - Disclosure - Quarterly Operating Results (Unaudited) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/QuarterlyOperatingResultsUnauditedTables</Role>
      <ShortName>Quarterly Operating Results (Unaudited) (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2328301 - Schedule - Schedule I - Condensed Financial Information of Parent Company (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ScheduleICondensedFinancialInformationOfParentCompanyTables</Role>
      <ShortName>Schedule I - Condensed Financial Information of Parent Company (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2401403 - Disclosure - Summary of the Business and Significant Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SummaryOfBusinessAndSignificantAccountingPoliciesDetails</Role>
      <ShortName>Summary of the Business and Significant Accounting Policies (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2401404 - Disclosure - Summary of the Business and Significant Accounting Policies (Inventories/Depreciation and Amortization) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SummaryOfBusinessAndSignificantAccountingPoliciesInventoriesDepreciationAndAmortizationDetails</Role>
      <ShortName>Summary of the Business and Significant Accounting Policies (Inventories/Depreciation and Amortization) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2402402 - Disclosure - Segment Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SegmentInformationDetails</Role>
      <ShortName>Segment Information (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2402403 - Disclosure - Segment Information (Narrative and Major Customers) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SegmentInformationNarrativeAndMajorCustomersDetails</Role>
      <ShortName>Segment Information (Narrative and Major Customers) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2404401 - Disclosure - Sale of First Choice (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SaleOfFirstChoiceDetails</Role>
      <ShortName>Sale of First Choice (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Regulatory Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/RegulatoryAssetsAndLiabilitiesDetails</Role>
      <ShortName>Regulatory Assets and Liabilities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2406401 - Disclosure - Stockholders' Equity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/StockholdersEquityDetails</Role>
      <ShortName>Stockholders' Equity (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - Financing (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FinancingDetails</Role>
      <ShortName>Financing (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2407403 - Disclosure - Financing Short-term Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FinancingShortTermDebtDetails</Role>
      <ShortName>Financing Short-term Debt (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2407404 - Disclosure - Financing Schedule of Long-term Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FinancingScheduleOfLongTermDebtDetails</Role>
      <ShortName>Financing Schedule of Long-term Debt (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2407405 - Disclosure - Financing Schedule of Long-term Debt Maturities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FinancingScheduleOfLongTermDebtMaturitiesDetails</Role>
      <ShortName>Financing Schedule of Long-term Debt Maturities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - Lease Commitments Narratives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/LeaseCommitmentsNarrativesDetails</Role>
      <ShortName>Lease Commitments Narratives (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>2408403 - Disclosure - Lease Commitments Schedule of Rent Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/LeaseCommitmentsScheduleOfRentExpenseDetails</Role>
      <ShortName>Lease Commitments Schedule of Rent Expense (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>2408404 - Disclosure - Lease Commitments Schedule of Future Minimum Rental Payments for Operating Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/LeaseCommitmentsScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesDetails</Role>
      <ShortName>Lease Commitments Schedule of Future Minimum Rental Payments for Operating Leases (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - Fair Value of Derivative and Other Financial Instruments, Derivative Balance Sheet Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FairValueOfDerivativeAndOtherFinancialInstrumentsDerivativeBalanceSheetInformationDetails</Role>
      <ShortName>Fair Value of Derivative and Other Financial Instruments, Derivative Balance Sheet Information (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - Fair Value of Derivative and Other Financial Instruments, Statement of Earnings Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FairValueOfDerivativeAndOtherFinancialInstrumentsStatementOfEarningsInformationDetails</Role>
      <ShortName>Fair Value of Derivative and Other Financial Instruments, Statement of Earnings Information (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>2409404 - Disclosure - Fair Value of Derivative and Other Financial Instruments, Margin, Notional Amounts, Credit Rating (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FairValueOfDerivativeAndOtherFinancialInstrumentsMarginNotionalAmountsCreditRatingDetails</Role>
      <ShortName>Fair Value of Derivative and Other Financial Instruments, Margin, Notional Amounts, Credit Rating (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>2409405 - Disclosure - Fair Value of Derivative and Other Financial Instruments, Sale of Power (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FairValueOfDerivativeAndOtherFinancialInstrumentsSaleOfPowerDetails</Role>
      <ShortName>Fair Value of Derivative and Other Financial Instruments, Sale of Power (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>2409406 - Disclosure - Fair Value of Derivative and Other Financial Instruments, Available for Sale Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FairValueOfDerivativeAndOtherFinancialInstrumentsAvailableForSaleSecuritiesDetails</Role>
      <ShortName>Fair Value of Derivative and Other Financial Instruments, Available for Sale Securities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>2409407 - Disclosure - Fair Value of Derivative and Other Financial Instruments, Debt Maturities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FairValueOfDerivativeAndOtherFinancialInstrumentsDebtMaturitiesDetails</Role>
      <ShortName>Fair Value of Derivative and Other Financial Instruments, Debt Maturities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>2409408 - Disclosure - Fair Value of Derivative and Other Financial Instruments, Recurring (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FairValueOfDerivativeAndOtherFinancialInstrumentsRecurringDetails</Role>
      <ShortName>Fair Value of Derivative and Other Financial Instruments, Recurring (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>2409409 - Disclosure - Fair Value of Derivative and Other Financial Instruments, Defined Benefit Plans Disclosure (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/FairValueOfDerivativeAndOtherFinancialInstrumentsDefinedBenefitPlansDisclosureDetails</Role>
      <ShortName>Fair Value of Derivative and Other Financial Instruments, Defined Benefit Plans Disclosure (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Variable Interest Entities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/VariableInterestEntitiesDetails</Role>
      <ShortName>Variable Interest Entities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>2412402 - Disclosure - Earnings and Dividends Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/EarningsAndDividendsPerShareDetails</Role>
      <ShortName>Earnings and Dividends Per Share (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - Income Taxes Schedule of Components of Income Tax Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/IncomeTaxesScheduleOfComponentsOfIncomeTaxExpenseDetails</Role>
      <ShortName>Income Taxes Schedule of Components of Income Tax Expense (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>2413403 - Disclosure - Income Taxes Schedule of Effective Income Tax Rate Reconciliation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/IncomeTaxesScheduleOfEffectiveIncomeTaxRateReconciliationDetails</Role>
      <ShortName>Income Taxes Schedule of Effective Income Tax Rate Reconciliation (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>2413404 - Disclosure - Income Taxes Schedule of Deferred Tax Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/IncomeTaxesScheduleOfDeferredTaxAssetsAndLiabilitiesDetails</Role>
      <ShortName>Income Taxes Schedule of Deferred Tax Assets and Liabilities (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>2413405 - Disclosure - Income Taxes Schedule of Deferred Income Tax Components (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/IncomeTaxesScheduleOfDeferredIncomeTaxComponentsDetails</Role>
      <ShortName>Income Taxes Schedule of Deferred Income Tax Components (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>2413406 - Disclosure - Income Taxes Summary of Income Tax Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/IncomeTaxesSummaryOfIncomeTaxContingenciesDetails</Role>
      <ShortName>Income Taxes Summary of Income Tax Contingencies (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>2413407 - Disclosure - Income Taxes Interest Expense (Income) Related to Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/IncomeTaxesInterestExpenseIncomeRelatedToIncomeTaxesDetails</Role>
      <ShortName>Income Taxes Interest Expense (Income) Related to Income Taxes (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>2413408 - Disclosure - Income Taxes Accumulated Accrued Interest Receivable (Payable) Related to Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/IncomeTaxesAccumulatedAccruedInterestReceivablePayableRelatedToIncomeTaxesDetails</Role>
      <ShortName>Income Taxes Accumulated Accrued Interest Receivable (Payable) Related to Income Taxes (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>2413409 - Disclosure - Income Taxes Carryforwards (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/IncomeTaxesCarryforwardsDetails</Role>
      <ShortName>Income Taxes Carryforwards (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - Pension and Other Postretirement Benefits Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/PensionAndOtherPostretirementBenefitsNarrativeDetails</Role>
      <ShortName>Pension and Other Postretirement Benefits Narrative (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>2414403 - Disclosure - Pension and Other Postretirement Benefits APBO, PBO, Fair Value of Plan Assets, and Funded Status of the Plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/PensionAndOtherPostretirementBenefitsApboPboFairValueOfPlanAssetsAndFundedStatusOfPlansDetails</Role>
      <ShortName>Pension and Other Postretirement Benefits APBO, PBO, Fair Value of Plan Assets, and Funded Status of the Plans (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>2414404 - Disclosure - Pension and Other Postretirement Benefits Pre-Tax Information about Prior Service Cost and Net Actuarial (Gain) loss in AOCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/PensionAndOtherPostretirementBenefitsPreTaxInformationAboutPriorServiceCostAndNetActuarialGainLossInAociDetails</Role>
      <ShortName>Pension and Other Postretirement Benefits Pre-Tax Information about Prior Service Cost and Net Actuarial (Gain) loss in AOCI (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>2414405 - Disclosure - Pension and Other Postretirement Benefits Components of Net Periodic Benefit Cost (Income) Recognized (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/PensionAndOtherPostretirementBenefitsComponentsOfNetPeriodicBenefitCostIncomeRecognizedDetails</Role>
      <ShortName>Pension and Other Postretirement Benefits Components of Net Periodic Benefit Cost (Income) Recognized (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>2414406 - Disclosure - Pension and Other Postretirement Benefits Assumptions Used (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/PensionAndOtherPostretirementBenefitsAssumptionsUsedDetails</Role>
      <ShortName>Pension and Other Postretirement Benefits Assumptions Used (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>2414407 - Disclosure - Pension and Other Postretirement Benefits Pension Benefit Payments are Expected to be Paid (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/PensionAndOtherPostretirementBenefitsPensionBenefitPaymentsAreExpectedToBePaidDetails</Role>
      <ShortName>Pension and Other Postretirement Benefits Pension Benefit Payments are Expected to be Paid (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>2414408 - Disclosure - Pension and Other Postretirement Benefits Assumed Health Care Cost Trend Rates and Impact of a One-Percentage-Point Change in Assumed Health Care Cost Trend Rates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/PensionAndOtherPostretirementBenefitsAssumedHealthCareCostTrendRatesAndImpactOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesDetails</Role>
      <ShortName>Pension and Other Postretirement Benefits Assumed Health Care Cost Trend Rates and Impact of a One-Percentage-Point Change in Assumed Health Care Cost Trend Rates (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>2414409 - Disclosure - Pension and Other Postretirement Benefits Other Postretirement Benefits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/PensionAndOtherPostretirementBenefitsOtherPostretirementBenefitsDetails</Role>
      <ShortName>Pension and Other Postretirement Benefits Other Postretirement Benefits (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>2415402 - Disclosure - Stock-Based Compensation Plans Performance Equity Plan/ Accounting for Stock Awards and ESPP (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/StockBasedCompensationPlansPerformanceEquityPlanAccountingForStockAwardsAndEsppDetails</Role>
      <ShortName>Stock-Based Compensation Plans Performance Equity Plan/ Accounting for Stock Awards and ESPP (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>2415403 - Disclosure - Stock-Based Compensation Plans Weighted Average Assumptions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/StockBasedCompensationPlansWeightedAverageAssumptionsDetails</Role>
      <ShortName>Stock-Based Compensation Plans Weighted Average Assumptions (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>2415404 - Disclosure - Stock-Based Compensation Plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/StockBasedCompensationPlansDetails</Role>
      <ShortName>Stock-Based Compensation Plans (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>2416402 - Disclosure - Construction Program and Jointly-Owned Electric Generating Plants Construction Program and Jointly-Owned Electric Generating Plants (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ConstructionProgramAndJointlyOwnedElectricGeneratingPlantsConstructionProgramAndJointlyOwnedElectricGeneratingPlantsDetails</Role>
      <ShortName>Construction Program and Jointly-Owned Electric Generating Plants Construction Program and Jointly-Owned Electric Generating Plants (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>2416403 - Disclosure - Summary of Budgeted Construction Expenditures (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/SummaryOfBudgetedConstructionExpendituresDetails</Role>
      <ShortName>Summary of Budgeted Construction Expenditures (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>2417402 - Disclosure - Asset Retirement Obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/AssetRetirementObligationsDetails</Role>
      <ShortName>Asset Retirement Obligations (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>2418401 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/CommitmentsAndContingenciesDetails</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>2419401 - Disclosure - Regulatory and Rate Matters (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/RegulatoryAndRateMattersDetails</Role>
      <ShortName>Regulatory and Rate Matters (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>2420402 - Disclosure - Related Party Transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/RelatedPartyTransactionsDetails</Role>
      <ShortName>Related Party Transactions (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>2422402 - Disclosure - Accumulated Other Comprehensive Income (Loss) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/AccumulatedOtherComprehensiveIncomeLossDetails</Role>
      <ShortName>Accumulated Other Comprehensive Income (Loss) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>2426401 - Disclosure - Goodwill; Impairments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/GoodwillImpairmentsDetails</Role>
      <ShortName>Goodwill; Impairments (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>2427402 - Disclosure - Quarterly Operating Results (Unaudited) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/QuarterlyOperatingResultsUnauditedDetails</Role>
      <ShortName>Quarterly Operating Results (Unaudited) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>2428402 - Schedule - Schedule I - Condensed Financial Information of Parent Company (Statements of Earnings) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ScheduleICondensedFinancialInformationOfParentCompanyStatementsOfEarningsDetails</Role>
      <ShortName>Schedule I - Condensed Financial Information of Parent Company (Statements of Earnings) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>2428403 - Schedule - Schedule I - Condensed Financial Information of Parent Company (Statement of Cash flow) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ScheduleICondensedFinancialInformationOfParentCompanyStatementOfCashFlowDetails</Role>
      <ShortName>Schedule I - Condensed Financial Information of Parent Company (Statement of Cash flow) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R104.htm</HtmlFileName>
      <LongName>2428404 - Schedule - Schedule I - Condensed Financial Information of Parent Company (Balance Sheets) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ScheduleICondensedFinancialInformationOfParentCompanyBalanceSheetsDetails</Role>
      <ShortName>Schedule I - Condensed Financial Information of Parent Company (Balance Sheets) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R105.htm</HtmlFileName>
      <LongName>2428405 - Schedule - Schedule I - Condensed Financial Information of Parent Company (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ScheduleICondensedFinancialInformationOfParentCompanyParentheticalDetails</Role>
      <ShortName>Schedule I - Condensed Financial Information of Parent Company (Parenthetical) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>2429401 - Schedule - Schedule II - Valuation and Qualifying Accounts (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.pnmresources.com/role/ScheduleIiValuationAndQualifyingAccountsDetails</Role>
      <ShortName>Schedule II - Valuation and Qualifying Accounts (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Element pnm_AnnualFeeNuclearWasteDisposal had a mix of decimals attribute values: -5 0.</Log>
    <Log type="Info">Element pnm_EstimatedInstallationCapitalCosts had a mix of decimals attribute values: -6 -5.</Log>
    <Log type="Info">Element pnm_PublicUtilitiesEstimatedratebasevalueat112018 had a mix of decimals attribute values: -6 -5.</Log>
    <Log type="Info">Element pnm_PublicUtilitiesOwnershipPercentage had a mix of decimals attribute values: 2 3.</Log>
    <Log type="Info">Element pnm_PublicUtilitiesReasonableCostThreshold had a mix of decimals attribute values: 0 2.</Log>
    <Log type="Info">Element us-gaap_DebtInstrumentFaceAmount had a mix of decimals attribute values: -5 0.</Log>
    <Log type="Info">Element us-gaap_DebtWeightedAverageInterestRate had a mix of decimals attribute values: 3 4.</Log>
    <Log type="Info">Element us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets had a mix of decimals attribute values: 3 4.</Log>
    <Log type="Info">Element us-gaap_DerivativeAssetsCurrent had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">Element us-gaap_NotesPayableRelatedPartiesClassifiedCurrent had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_ProceedsFromShortTermDebt had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_ShortTermBorrowings had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Consolidated Statements of Cash Flows (USD $)' have maximum duration 365 days and at least 121 values. Shorter duration columns must have at least one fourth (30) as many values. Column '1/1/2013 - 3/31/2013' is shorter (89 days) and has only 5 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Consolidated Statements of Cash Flows (USD $)' have maximum duration 365 days and at least 121 values. Shorter duration columns must have at least one fourth (30) as many values. Column '4/1/2013 - 6/30/2013' is shorter (90 days) and has only 2 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Consolidated Statements of Cash Flows (USD $)' have maximum duration 365 days and at least 121 values. Shorter duration columns must have at least one fourth (30) as many values. Column '7/1/2013 - 9/30/2013' is shorter (91 days) and has only 2 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Consolidated Statements of Cash Flows (USD $)' have maximum duration 365 days and at least 121 values. Shorter duration columns must have at least one fourth (30) as many values. Column '10/1/2013 - 12/31/2013' is shorter (91 days) and has only 5 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Consolidated Statements of Cash Flows (USD $)' have maximum duration 365 days and at least 121 values. Shorter duration columns must have at least one fourth (30) as many values. Column '1/1/2014 - 3/31/2014' is shorter (89 days) and has only 5 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Consolidated Statements of Cash Flows (USD $)' have maximum duration 365 days and at least 121 values. Shorter duration columns must have at least one fourth (30) as many values. Column '4/1/2014 - 6/30/2014' is shorter (90 days) and has only 2 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Consolidated Statements of Cash Flows (USD $)' have maximum duration 365 days and at least 121 values. Shorter duration columns must have at least one fourth (30) as many values. Column '7/1/2014 - 9/30/2014' is shorter (91 days) and has only 2 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Consolidated Statements of Cash Flows (USD $)' have maximum duration 365 days and at least 121 values. Shorter duration columns must have at least one fourth (30) as many values. Column '10/1/2014 - 12/31/2014' is shorter (91 days) and has only 5 values, so it is being removed.</Log>
    <Log type="Info">'Monetary' elements on report '1004000 - Statement - Consolidated Balance Sheets' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2406401 - Disclosure - Stockholders' Equity (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2407402 - Disclosure - Financing (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2407403 - Disclosure - Financing Short-term Debt (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2408402 - Disclosure - Lease Commitments Narratives (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2409406 - Disclosure - Fair Value of Derivative and Other Financial Instruments, Available for Sale Securities (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2410402 - Disclosure - Variable Interest Entities (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Shares' elements on report '2412402 - Disclosure - Earnings and Dividends Per Share (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2413406 - Disclosure - Income Taxes Summary of Income Tax Contingencies (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2413409 - Disclosure - Income Taxes Carryforwards (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2414402 - Disclosure - Pension and Other Postretirement Benefits Narrative (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2417402 - Disclosure - Asset Retirement Obligations (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2418401 - Disclosure - Commitments and Contingencies (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2419401 - Disclosure - Regulatory and Rate Matters (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2426401 - Disclosure - Goodwill; Impairments (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Schedule I - Condensed Financial Information of Parent Company (Statement of Cash flow) (Details) (USD $)' have maximum duration 365 days and at least 55 values. Shorter duration columns must have at least one fourth (13) as many values. Column '1/1/2013 - 3/31/2013' is shorter (89 days) and has only 3 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Schedule I - Condensed Financial Information of Parent Company (Statement of Cash flow) (Details) (USD $)' have maximum duration 365 days and at least 55 values. Shorter duration columns must have at least one fourth (13) as many values. Column '4/1/2013 - 6/30/2013' is shorter (90 days) and has only 1 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Schedule I - Condensed Financial Information of Parent Company (Statement of Cash flow) (Details) (USD $)' have maximum duration 365 days and at least 55 values. Shorter duration columns must have at least one fourth (13) as many values. Column '7/1/2013 - 9/30/2013' is shorter (91 days) and has only 1 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Schedule I - Condensed Financial Information of Parent Company (Statement of Cash flow) (Details) (USD $)' have maximum duration 365 days and at least 55 values. Shorter duration columns must have at least one fourth (13) as many values. Column '10/1/2013 - 12/31/2013' is shorter (91 days) and has only 3 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Schedule I - Condensed Financial Information of Parent Company (Statement of Cash flow) (Details) (USD $)' have maximum duration 365 days and at least 55 values. Shorter duration columns must have at least one fourth (13) as many values. Column '1/1/2014 - 3/31/2014' is shorter (89 days) and has only 3 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Schedule I - Condensed Financial Information of Parent Company (Statement of Cash flow) (Details) (USD $)' have maximum duration 365 days and at least 55 values. Shorter duration columns must have at least one fourth (13) as many values. Column '4/1/2014 - 6/30/2014' is shorter (90 days) and has only 1 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Schedule I - Condensed Financial Information of Parent Company (Statement of Cash flow) (Details) (USD $)' have maximum duration 365 days and at least 55 values. Shorter duration columns must have at least one fourth (13) as many values. Column '7/1/2014 - 9/30/2014' is shorter (91 days) and has only 1 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'Schedule I - Condensed Financial Information of Parent Company (Statement of Cash flow) (Details) (USD $)' have maximum duration 365 days and at least 55 values. Shorter duration columns must have at least one fourth (13) as many values. Column '10/1/2014 - 12/31/2014' is shorter (91 days) and has only 3 values, so it is being removed.</Log>
    <Log type="Info">Process Flow-Through: 1001000 - Statement - Consolidated Statements of Earnings</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Dec. 31, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Sep. 30, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Jun. 30, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Mar. 31, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Dec. 31, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Sep. 30, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Jun. 30, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Mar. 31, 2013'</Log>
    <Log type="Info">Process Flow-Through: 1002000 - Statement - Consolidated Statements of Comprehensive Income</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Dec. 31, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Sep. 30, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Jun. 30, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Mar. 31, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Dec. 31, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Sep. 30, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Jun. 30, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Mar. 31, 2013'</Log>
    <Log type="Info">Process Flow-Through: 1002501 - Statement - Consolidated Statements of Comprehensive Income (Loss) (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1003000 - Statement - Consolidated Statements of Cash Flows</Log>
    <Log type="Info">Process Flow-Through: 1004000 - Statement - Consolidated Balance Sheets</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2011'</Log>
    <Log type="Info">Process Flow-Through: 1004501 - Statement - Consolidated Balance Sheets (Parenthetical)</Log>
  </Logs>
  <InputFiles>
    <File>pnm-20141231.xml</File>
    <File>pnm-20141231.xsd</File>
    <File>pnm-20141231_cal.xml</File>
    <File>pnm-20141231_def.xml</File>
    <File>pnm-20141231_lab.xml</File>
    <File>pnm-20141231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
