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Fair Value of Derivative and Other Financial Instruments - Recurring (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
PNMR and PNM [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 257,464us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember	$ 250,145us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember
PNM Resources [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	2,322,072us-gaap_LongTermDebtFairValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	2,173,117us-gaap_LongTermDebtFairValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Investment In PVNGS lessor notes	17,173pnm_InvestmentInLessorNotesFairValueDisclosure / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	32,836pnm_InvestmentInLessorNotesFairValueDisclosure / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Other investments	1,135pnm_OtherInvestmentsFairValueDisclosure / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	2,375pnm_OtherInvestmentsFairValueDisclosure / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
PNM Resources [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Investment In PVNGS lessor notes	0pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	0pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Other investments	509pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	639pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
PNM Resources [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	2,322,072us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	2,173,117us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Investment In PVNGS lessor notes	0pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	0pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Other investments	0pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	0pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
PNM Resources [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Investment In PVNGS lessor notes	17,173pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	32,836pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Other investments	626pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	1,736pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Public Service Company of New Mexico [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	1,627,751us-gaap_LongTermDebtFairValue / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	1,624,222us-gaap_LongTermDebtFairValue / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Investment In PVNGS lessor notes	17,173pnm_InvestmentInLessorNotesFairValueDisclosure / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	32,836pnm_InvestmentInLessorNotesFairValueDisclosure / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Other investments	267pnm_OtherInvestmentsFairValueDisclosure / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	397pnm_OtherInvestmentsFairValueDisclosure / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Public Service Company of New Mexico [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Investment In PVNGS lessor notes	0pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	0pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Other investments	267pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	397pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Public Service Company of New Mexico [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	1,627,751us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	1,624,222us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Investment In PVNGS lessor notes	0pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	0pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Other investments	0pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	0pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Public Service Company of New Mexico [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Investment In PVNGS lessor notes	17,173pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	32,836pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Other investments	0pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	0pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Texas-New Mexico Power Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	427,356us-gaap_LongTermDebtFairValue / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	427,356us-gaap_LongTermDebtFairValue / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember
Other investments	242pnm_OtherInvestmentsFairValueDisclosure / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	242pnm_OtherInvestmentsFairValueDisclosure / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember
Texas-New Mexico Power Company [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember
Other investments	242pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	242pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember
Texas-New Mexico Power Company [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	427,356us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	427,356us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember
Other investments	0pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	0pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember
Texas-New Mexico Power Company [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	0us-gaap_LongTermDebtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember
Other investments	0pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	0pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember
Reported Value Measurement [Member] | PNM Resources [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	2,125,007us-gaap_LongTermDebtFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	1,975,090us-gaap_LongTermDebtFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Investment In PVNGS lessor notes	16,806pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	31,232pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Other investments	509pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember	1,762pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Reported Value Measurement [Member] | Public Service Company of New Mexico [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	1,490,666us-gaap_LongTermDebtFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	1,490,657us-gaap_LongTermDebtFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Investment In PVNGS lessor notes	16,806pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	31,232pnm_InvestmentInLessorNotesFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Other investments	267pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	397pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Reported Value Measurement [Member] | Texas-New Mexico Power Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	365,575us-gaap_LongTermDebtFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	365,667us-gaap_LongTermDebtFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember
Other investments	242pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	242pnm_OtherInvestmentsFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember
Cash and equivalents [Member] | PNMR and PNM [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	5,142us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashAndCashEquivalentsMember	8,276us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashAndCashEquivalentsMember
Domestic value [Member] | PNMR and PNM [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	46,129us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = pnm_DomesticValueMember	45,340us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = pnm_DomesticValueMember
Domestic growth [Member] | PNMR and PNM [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	78,013us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = pnm_DomesticGrowthMember	74,053us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = pnm_DomesticGrowthMember
International and other [Member] | PNMR and PNM [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	17,478us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = pnm_MultinationalMember	16,599us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = pnm_MultinationalMember
U.S. Government [Member] | PNMR and PNM [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	21,912us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember	22,563us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember
Municipals [Member] | PNMR and PNM [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	73,554us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember	68,973us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MunicipalBondsMember
Corporate and other [Member] | PNMR and PNM [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	15,236us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_OtherDebtSecuritiesMember	14,341us-gaap_AvailableForSaleSecurities / dei_LegalEntityAxis = pnm_PnmrAndPnmMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_OtherDebtSecuritiesMember
Fair Value, Measurements, Recurring [Member] | PNMR and PNM [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	257,464us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember	250,145us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember
Fair Value, Measurements, Recurring [Member] | PNMR and PNM [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	172,266us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember	169,919us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember
Fair Value, Measurements, Recurring [Member] | PNMR and PNM [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	85,198us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember	80,226us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember
Fair Value, Measurements, Recurring [Member] | Commodity Contract [Member] | PNMR and PNM [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets	9,342us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember	11,232us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember
Commodity derivative instruments, Liabilities	(1,512)us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember	(1,686)us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember
Commodity derivative instruments, Net	7,830us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember	9,546us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember
Fair Value, Measurements, Recurring [Member] | Commodity Contract [Member] | PNMR and PNM [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets	0us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember	0us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / dei_LegalEntityAxis = pnm_PnmrAndPnmMember
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Measurements, Recurring [Member] | International and other [Member] | PNMR and PNM [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Investment In Lessor Notes, Fair Value Disclosure

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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