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Regulatory and Rate Matters (Details) (USD $) | 12 Months Ended | 1 Months Ended | 3 Months Ended | 12 Months Ended | 0 Months Ended | 12 Months Ended | 0 Months Ended | 1 Months Ended | 6 Months Ended | 12 Months Ended | 6 Months Ended | 4 Months Ended |  |  |
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Dec. 31, 2014 | Dec. 31, 2011 | Dec. 31, 2014 MW | Dec. 31, 2013 | Dec. 31, 2012 | Oct. 05, 2012 | Oct. 06, 2014 | Dec. 31, 2011 | Dec. 06, 2012 | Jul. 31, 2011 | Jun. 30, 2012 | Sep. 07, 2014 | Mar. 12, 2014 | Sep. 16, 2013 | Mar. 19, 2013 | Dec. 31, 2015 | Sep. 15, 2015 | Mar. 15, 2015 | Jun. 17, 2015 | Jan. 31, 2012 | Feb. 20, 2015 customer | Feb. 17, 2015
Public Service Company of New Mexico [Member] | 2014 Electric Rate Case [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount | $ 107,400,000us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2014ElectricRateCaseMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Requested Return on Equity, Percentage | 10.50%us-gaap_PublicUtilitiesRequestedReturnOnEquityPercentage / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2014ElectricRateCaseMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Average customer bill increase percentage | 7.69%pnm_PublicUtilitiesAveragecustomerbillincreasepercentage / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2014ElectricRateCaseMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Percentage of requested rate increase pertaining to infrastructure investments | 92.00%pnm_PublicUtilitiesPercentageofrequestedrateincreasepertainingtoinfrastructureinvestments / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2014ElectricRateCaseMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilites, Additional Renewable Procurements Spending Required by NMPRC |  | 900,000pnm_PublicUtilitesAdditionalRenewableProcurementsSpendingRequiredByNmprc / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Mega Watts of Solar Photovoltaic Capacity | 20pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 20pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Estimated Cost of Mega Watts of Solar Photovoltaic Capacity |  |  | 45,500,000pnm_PublicUtilitiesEstimatedCostOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Final Cost of Solar Photovoltaic Capacity |  |  |  | 48,900,000pnm_PublicUtilitiesFinalCostofSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Mega Watts of Solar Photovoltaic Capacity, Current Output | 4pnm_PublicUtilitiesNumberofMegaWattsofSolarPhotovoltaicCapacityCurrentOutput / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 4pnm_PublicUtilitiesNumberofMegaWattsofSolarPhotovoltaicCapacityCurrentOutput / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Mega Watts of Solar Photovoltaic Capacity, Expected Output | 10pnm_PublicUtilitiesNumberofMegaWattsofSolarPhotovoltaicCapacityExpectedOutput / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 10pnm_PublicUtilitiesNumberofMegaWattsofSolarPhotovoltaicCapacityExpectedOutput / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Reasonable Cost Threshold | 3.00%pnm_PublicUtilitiesReasonableCostThreshold / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 3.00%pnm_PublicUtilitiesReasonableCostThreshold / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Reasonable Cost Threshold | 3.00%pnm_PublicUtilitiesReasonableCostThreshold / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 3.00%pnm_PublicUtilitiesReasonableCostThreshold / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Wind Energy [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Required Percentage of Diversification | 30.00%pnm_PublicUtilitiesRequiredPercentageOfDiversification / pnm_DiversificationByTypeAxis = pnm_WindEnergyMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 30.00%pnm_PublicUtilitiesRequiredPercentageOfDiversification / pnm_DiversificationByTypeAxis = pnm_WindEnergyMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Solar Energy [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Required Percentage of Diversification | 20.00%pnm_PublicUtilitiesRequiredPercentageOfDiversification / pnm_DiversificationByTypeAxis = pnm_SolarEnergyMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 20.00%pnm_PublicUtilitiesRequiredPercentageOfDiversification / pnm_DiversificationByTypeAxis = pnm_SolarEnergyMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Renewable Technologies [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Required Percentage of Diversification | 5.00%pnm_PublicUtilitiesRequiredPercentageOfDiversification / pnm_DiversificationByTypeAxis = pnm_RenewableTechnologiesMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 5.00%pnm_PublicUtilitiesRequiredPercentageOfDiversification / pnm_DiversificationByTypeAxis = pnm_RenewableTechnologiesMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Distributed Generation [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Required Percentage of Diversification | 1.50%pnm_PublicUtilitiesRequiredPercentageOfDiversification / pnm_DiversificationByTypeAxis = pnm_DistributedGenerationMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 1.50%pnm_PublicUtilitiesRequiredPercentageOfDiversification / pnm_DiversificationByTypeAxis = pnm_DistributedGenerationMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Future Required Percentage of Diversification | 3.00%pnm_PublicUtilitiesFutureRequiredPercentageofDiversification / pnm_DiversificationByTypeAxis = pnm_DistributedGenerationMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 3.00%pnm_PublicUtilitiesFutureRequiredPercentageofDiversification / pnm_DiversificationByTypeAxis = pnm_DistributedGenerationMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Required Percentage by 2011 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Required Percentage of Renewable Energy in Portfolio to Electric Sales | 10.00%pnm_PublicUtilitiesRequiredPercentageOfRenewableEnergyInPortfolioToElectricSales / pnm_DateOfRegulatoryActionAxis = pnm_RequiredPercentageBy2011Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 10.00%pnm_PublicUtilitiesRequiredPercentageOfRenewableEnergyInPortfolioToElectricSales / pnm_DateOfRegulatoryActionAxis = pnm_RequiredPercentageBy2011Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Required Percentage by 2015 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Required Percentage of Renewable Energy in Portfolio to Electric Sales | 15.00%pnm_PublicUtilitiesRequiredPercentageOfRenewableEnergyInPortfolioToElectricSales / pnm_DateOfRegulatoryActionAxis = pnm_RequiredPercentageBy2015Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 15.00%pnm_PublicUtilitiesRequiredPercentageOfRenewableEnergyInPortfolioToElectricSales / pnm_DateOfRegulatoryActionAxis = pnm_RequiredPercentageBy2015Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Required Percentage by 2020 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Required Percentage of Renewable Energy in Portfolio to Electric Sales | 20.00%pnm_PublicUtilitiesRequiredPercentageOfRenewableEnergyInPortfolioToElectricSales / pnm_DateOfRegulatoryActionAxis = pnm_RequiredPercentageBy2020Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  | 20.00%pnm_PublicUtilitiesRequiredPercentageOfRenewableEnergyInPortfolioToElectricSales / pnm_DateOfRegulatoryActionAxis = pnm_RequiredPercentageBy2020Member / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard Supplemental Procurement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Mega Watts of Solar Photovoltaic Capacity | 2pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardSupplementalProcurementMember |  | 2pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardSupplementalProcurementMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Estimated Cost of Mega Watts of Solar Photovoltaic Capacity |  |  | 4,500,000pnm_PublicUtilitiesEstimatedCostOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardSupplementalProcurementMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard Supplemental Procurement Reduction [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Mega Watts of Solar Photovoltaic Capacity | 1.5pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardSupplementalProcurementReductionMember |  | 1.5pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardSupplementalProcurementReductionMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard Supplemental Procurement Reduction [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Mega Watts of Solar Photovoltaic Capacity | 2pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardSupplementalProcurementReductionMember |  | 2pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandardSupplementalProcurementReductionMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard 2014 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Mega Watts of Solar Photovoltaic Capacity | 23pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2014Member |  | 23pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2014Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Estimated Cost of Mega Watts of Solar Photovoltaic Capacity | 46,700,000pnm_PublicUtilitiesEstimatedCostOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2014Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Wind Capacity Planned Purchase Agreement Term | 20 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Mega Watts of Wind Energy Capacity | 102pnm_PublicUtilitiesNumberofMegaWattsofWindEnergyCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2014Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, First Year Cost of Wind Capacity Planned Purchase Agreement | 5,800,000.0pnm_PublicUtilitiesFirstYearCostofWindCapacityPlannedPurchaseAgreement / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2014Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard 2015 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Mega Watts of Solar Photovoltaic Capacity | 40pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2015Member |  | 40pnm_PublicUtilitiesNumberOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2015Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Estimated Cost of Mega Watts of Solar Photovoltaic Capacity | 79,300,000pnm_PublicUtilitiesEstimatedCostOfMegaWattsOfSolarPhotovoltaicCapacity / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2015Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved cost per MWh for additional necessary procurements to comply with RPS | 4.25pnm_PublicUtilitiesApprovedcostperMWhforadditionalnecessaryprocurementstocomplywithRPS / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2015Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Revised cost per MWh for additional necessary procurements to comply with RPS | 3.00pnm_PublicUtilitiesApprovedRevisedcostperMWhforadditionalnecessaryprocurementstocomplywithRPS / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2015Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of MegaWatt Hours of renewable resources | 44,000pnm_PublicUtilitiesNumberofMegaWattHoursofrenewableresources / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2015Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Actual cost per MWh for additional necessary procurements to comply with RPS | 1.75pnm_PublicUtilitiesActualcostperMWhforadditionalnecessaryprocurementstocomplywithRPS / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewablePortfolioStandard2015Member |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | 2014 Wind generated Renewable Energy Credits [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Mega Watt Hours of Wind Generation | 50,000pnm_PublicUtilitiesNumberofMegaWattHoursofWindGeneration / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2014WindgeneratedRenewableEnergyCreditsMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | 2015 Wind generated Renewable Energy Credits [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Number of Mega Watt Hours of Wind Generation | 120,000pnm_PublicUtilitiesNumberofMegaWattHoursofWindGeneration / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2015WindgeneratedRenewableEnergyCreditsMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Energy Rider [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Revenue from Renewable energy rider | 34,300,000pnm_PublicUtilitiesRevenuefromRenewableenergyrider / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewableEnergyRiderMember |  |  | 23,700,000pnm_PublicUtilitiesRevenuefromRenewableenergyrider / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewableEnergyRiderMember | 6,400,000pnm_PublicUtilitiesRevenuefromRenewableenergyrider / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewableEnergyRiderMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Renewable Energy Rider [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Rider Condition of Earned Return on Jurisdictional Equity in 2013 | 10.50%pnm_PublicUtilitiesRiderConditionOfEarnedReturnOnJurisdictionalEquityIn2013 / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewableEnergyRiderMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Annual Revenue To be Collected Under 2015 Rider Rate | 44,700,000pnm_PublicUtilitiesAnnualRevenueTobeCollectedUnder2015RiderRate / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewableEnergyRiderMember |  | 44,700,000pnm_PublicUtilitiesAnnualRevenueTobeCollectedUnder2015RiderRate / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_RenewableEnergyRiderMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Energy Efficient and Load Management [Member] | Disincentives / Incentives Adder [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Program Costs Related To Energy Efficiency |  |  |  |  |  | 22,500,000pnm_PublicUtilitiesProgramCostsRelatedToEnergyEfficiency / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyAndLoadManagementMember / pnm_TypeOfRegulatoryCostAxis = pnm_DisincentivesIncentivesAdderMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Profit Incentive Adder Revenues Related To Energy Efficiency Program, Percentage of Program Costs | 7.60%pnm_PublicUtilitiesApprovedProfitIncentiveAdderRevenuesRelatedToEnergyEfficiencyProgramPercentageofProgramCosts / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyAndLoadManagementMember / pnm_TypeOfRegulatoryCostAxis = pnm_DisincentivesIncentivesAdderMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Profit Incentive Adder Revenues Related To Energy Efficiency Program |  |  |  | 1,700,000pnm_PublicUtilitiesApprovedProfitIncentiveAdderRevenuesRelatedToEnergyEfficiencyProgram / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyAndLoadManagementMember / pnm_TypeOfRegulatoryCostAxis = pnm_DisincentivesIncentivesAdderMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Energy Efficiency Incentive adder collected |  |  |  | 1,300,000pnm_PublicUtilitiesEnergyEfficiencyIncentiveaddercollected / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyAndLoadManagementMember / pnm_TypeOfRegulatoryCostAxis = pnm_DisincentivesIncentivesAdderMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | FPPAC Continuation Application [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Retention Percentage of Sales Margins | 10.00%pnm_PublicUtilitiesRetentionPercentageOfSalesMargins / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_FPPACContinuationApplicationMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Under-collected balance write-off |  |  |  | 10,500,000pnm_PublicUtilitiesUndercollectedbalancewriteoff / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_FPPACContinuationApplicationMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Under-recovery expected to be collected | 63,500,000pnm_PublicUtilitiesUnderrecoveryexpectedtobecollected / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_FPPACContinuationApplicationMember |  | 63,500,000pnm_PublicUtilitiesUnderrecoveryexpectedtobecollected / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_FPPACContinuationApplicationMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | FPPAC Continuation Application [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Fuel Costs to be Collected |  |  |  | 36,200,000pnm_PublicUtilitiesFuelCoststobeCollected / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_FPPACContinuationApplicationMember | 38,800,000pnm_PublicUtilitiesFuelCoststobeCollected / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_FPPACContinuationApplicationMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | 2014 Energy Efficiency and Load Management Program [Member] | Disincentives / Incentives Adder [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Program Costs Related To Energy Efficiency |  |  |  |  |  |  | 25,800,000pnm_PublicUtilitiesProgramCostsRelatedToEnergyEfficiency / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2014EnergyEfficiencyandLoadManagementProgramMember / pnm_TypeOfRegulatoryCostAxis = pnm_DisincentivesIncentivesAdderMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Proposed Profit Incentive Adder Revenues Related To Energy Efficiency Program | 2,100,000pnm_PublicUtilitiesProposedProfitIncentiveAdderRevenuesRelatedToEnergyEfficiencyProgram / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2014EnergyEfficiencyandLoadManagementProgramMember / pnm_TypeOfRegulatoryCostAxis = pnm_DisincentivesIncentivesAdderMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Anticipated future profit incentive 2015 | 1,700,000pnm_PublicUtilitiesAnticipatedfutureprofitincentive2015 / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2014EnergyEfficiencyandLoadManagementProgramMember / pnm_TypeOfRegulatoryCostAxis = pnm_DisincentivesIncentivesAdderMember |  | 1,700,000pnm_PublicUtilitiesAnticipatedfutureprofitincentive2015 / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2014EnergyEfficiencyandLoadManagementProgramMember / pnm_TypeOfRegulatoryCostAxis = pnm_DisincentivesIncentivesAdderMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Anticipated future profit incentive 2016 | 1,800,000pnm_PublicUtilitiesAnticipatedfutureprofitincentive2016 / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2014EnergyEfficiencyandLoadManagementProgramMember / pnm_TypeOfRegulatoryCostAxis = pnm_DisincentivesIncentivesAdderMember |  | 1,800,000pnm_PublicUtilitiesAnticipatedfutureprofitincentive2016 / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_A2014EnergyEfficiencyandLoadManagementProgramMember / pnm_TypeOfRegulatoryCostAxis = pnm_DisincentivesIncentivesAdderMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Nmprc Rulemaking on Disincentives to Energy Efficiency Programs [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Rate Rider Net Over-Recovery |  |  |  | 200,000pnm_PublicUtilitiesRateRiderNetOverRecovery / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_NmprcRulemakingOnDisincentivesToEnergyEfficiencyProgramsMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Rate Rider Program Costs Over-Recovery |  |  |  | 1,000,000pnm_PublicUtilitiesRateRiderProgramCostsOverRecovery / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_NmprcRulemakingOnDisincentivesToEnergyEfficiencyProgramsMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Rate Rider Incentives Under-Recovery |  |  |  | 800,000pnm_PublicUtilitiesRateRiderIncentivesUnderRecovery / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_NmprcRulemakingOnDisincentivesToEnergyEfficiencyProgramsMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Rate Rider Estimated Incentives Under-Recovery |  |  |  | 500,000pnm_PublicUtilitiesRateRiderEstimatedIncentivesUnderRecovery / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_NmprcRulemakingOnDisincentivesToEnergyEfficiencyProgramsMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | 2011 Integrated Resource Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Planning Period Covered of IRP | 20 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Transmission Rate Case [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | 11,100,000us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionRateCaseMember |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Return on Equity, Percentage |  |  |  |  |  |  |  | 12.25%us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionRateCaseMember |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Increase Annual Transmission Service Revenue |  |  |  | 2,900,000pnm_PublicUtilitiesIncreaseAnnualTransmissionServiceRevenue / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionRateCaseMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Wholesale Electric Transmission Rate Case [Member] [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount |  |  |  | 2,900,000us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_WholesaleElectricTransmissionRateCaseMemberMember | 3,200,000us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_WholesaleElectricTransmissionRateCaseMemberMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Return on Equity, Percentage |  |  |  | 10.81%us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_WholesaleElectricTransmissionRateCaseMemberMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Lease ownership percentage in EIP | 60.00%pnm_PublicUtilitiesLeaseOwnershipPercentageInEip / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_WholesaleElectricTransmissionRateCaseMemberMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved additional rate increase, Amount | 500,000pnm_PublicUtilitiesApprovedadditionalrateincreaseAmount / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_WholesaleElectricTransmissionRateCaseMemberMember |  |  | 1,300,000pnm_PublicUtilitiesApprovedadditionalrateincreaseAmount / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_WholesaleElectricTransmissionRateCaseMemberMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Firm Requirements Wholesale Power Rate Case, Navopache [Member] [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  | 8,700,000us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_FirmRequirementsWholesalePowerRateCaseNavopacheMemberMember |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  |  | 5,300,000us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_FirmRequirementsWholesalePowerRateCaseNavopacheMemberMember |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Regulatory Rate Increase |  |  |  |  |  |  |  | 39.80%us-gaap_PublicUtilitiesRequestedRateIncreaseDecreasePercentage / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_FirmRequirementsWholesalePowerRateCaseNavopacheMemberMember |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Firm Requirements Wholesale Power Rate Case [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Contract Extension |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |
Public Service Company of New Mexico [Member] | Firm Requirements Wholesale Power Contract, Gallup [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Revenue For Power Sold Under Specific Contract | 6,100,000pnm_PublicUtilitiesRevenueForPowerSoldUnderSpecificContract / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_FirmRequirementsWholesalePowerContractGallupMember |  |  | 11,700,000pnm_PublicUtilitiesRevenueForPowerSoldUnderSpecificContract / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_FirmRequirementsWholesalePowerContractGallupMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Texas-New Mexico Power Company [Member] | Advanced Meter System Deployment and Surcharge Request [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Deployment Costs |  |  |  |  |  |  |  |  |  | 113,400,000pnm_PublicUtilitiesApprovedDeploymentCosts / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Collection of Deployment Costs Through Surcharge Period |  |  |  |  |  |  |  |  |  | 12 years |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Completion Period of Advanced Meter Deployment |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Non-standard metering service cost total to be borne by opt-out customers |  |  |  | 200,000pnm_PublicUtilitiesNonstandardmeteringserviceProposedcosttotaltobebornebyoptoutcustomers / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Non-standard metering ongoing expenses total to be borne by opt-out customers |  |  |  | 500,000pnm_PublicUtilitiesNonstandardmeteringProposedongoingexpensestotaltobebornebyoptoutcustomers / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Non-standard metering ongoing expenses monthly charge |  |  |  | 38.99pnm_PublicUtilitiesNonstandardmeteringongoingexpensesProposedmonthlycharge / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Non-standard metering service cost total to be borne by opt-out customers | 200,000pnm_PublicUtilitiesNonstandardmeteringservicecosttotaltobebornebyoptoutcustomers / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  | 200,000pnm_PublicUtilitiesNonstandardmeteringservicecosttotaltobebornebyoptoutcustomers / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Non-standard metering ongoing expenses total to be borne by opt-out customers | 500,000pnm_PublicUtilitiesNonstandardmeteringongoingexpensestotaltobebornebyoptoutcustomers / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  | 500,000pnm_PublicUtilitiesNonstandardmeteringongoingexpensestotaltobebornebyoptoutcustomers / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Non-standard metering ongoing expenses monthly charge | 36.78pnm_PublicUtilitiesNonstandardmeteringongoingexpensesmonthlycharge / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  | 36.78pnm_PublicUtilitiesNonstandardmeteringongoingexpensesmonthlycharge / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Presumed number of customers that will elect non-standard meter service | 1,081pnm_Presumednumberofcustomersthatwillelectnonstandardmeterservice / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  | 1,081pnm_Presumednumberofcustomersthatwillelectnonstandardmeterservice / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Texas-New Mexico Power Company [Member] | Advanced Meter System Deployment and Surcharge Request [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Non-standard metering service cost, Proposed initial fee range |  |  |  | 142.84pnm_PublicUtilitiesNonstandardmeteringservicecostProposedinitialfeerange / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Non-standard metering service cost initial fee range | 63.97pnm_PublicUtilitiesNonstandardmeteringservicecostinitialfeerange / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  | 63.97pnm_PublicUtilitiesNonstandardmeteringservicecostinitialfeerange / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / us-gaap_RangeAxis = us-gaap_MinimumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Texas-New Mexico Power Company [Member] | Advanced Meter System Deployment and Surcharge Request [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Non-standard metering service cost, Proposed initial fee range |  |  |  | 247.48pnm_PublicUtilitiesNonstandardmeteringservicecostProposedinitialfeerange / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Non-standard metering service cost initial fee range | 168.61pnm_PublicUtilitiesNonstandardmeteringservicecostinitialfeerange / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  | 168.61pnm_PublicUtilitiesNonstandardmeteringservicecostinitialfeerange / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / us-gaap_RangeAxis = us-gaap_MaximumMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Texas-New Mexico Power Company [Member] | Ercot Transmission Rates [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Eliminated Recovery of Adder Revenue |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,600,000pnm_PublicUtilitiesResettlementawardofpreviouslyremandedrates / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_ErcotTransmissionRatesMember |  |
Public Utilities, Additional Transmission Costs Requested |  |  |  |  |  |  |  |  |  |  | 3,200,000pnm_PublicUtilitiesAdditionalTransmissionCostsRequested / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_ErcotTransmissionRatesMember |  |  |  |  |  |  |  |  |  |  |
Texas-New Mexico Power Company [Member] | Ercot Transmission Rates [Member] | PUCT staff agreed to interim rate relief that will permit TNMP to add uncontested costs to its existing TCRF [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Additional Transmission Costs |  |  |  | 1,600,000pnm_PublicUtilitiesApprovedAdditionalTransmissionCosts / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_ErcotTransmissionRatesMember / pnm_StatusOfRateMattersFilingAxis = pnm_PuctStaffAgreedToInterimRateReliefThatWillPermitTnmpToAddUncontestedCostsToItsExistingTcrfMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Texas-New Mexico Power Company [Member] | Energy Efficiency [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Program Implementation Costs | 5,600,000pnm_PublicUtilitiesApprovedProgramImplementationCosts / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyMember |  |  | 5,200,000pnm_PublicUtilitiesApprovedProgramImplementationCosts / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyMember | 3,400,000pnm_PublicUtilitiesApprovedProgramImplementationCosts / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Program Implementation Costs, Bonus | 1,500,000pnm_PublicUtilitiesApprovedProgramImplementationCostsBonus / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyMember |  |  |  | 300,000pnm_PublicUtilitiesApprovedProgramImplementationCostsBonus / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Unapproved 2015 Program Implementation Costs, Bonus | 700,000pnm_PublicUtilitiesUnapproved2015ProgramImplementationCostsBonus / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyMember |  | 700,000pnm_PublicUtilitiesUnapproved2015ProgramImplementationCostsBonus / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyMember | 1,500,000pnm_PublicUtilitiesUnapproved2015ProgramImplementationCostsBonus / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Unapproved 2015 Program Implementation Costs | 5,700,000pnm_PublicUtilitiesUnapproved2015ProgramImplementationCosts / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyMember |  | 5,700,000pnm_PublicUtilitiesUnapproved2015ProgramImplementationCosts / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Texas-New Mexico Power Company [Member] | Transmission Cost of Service Rates [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  |  |  |  |  | 18,200,000us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember | 18,100,000us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember | 21,900,000us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember | 26,400,000us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember |  |  |  |  |  |  |
Public Utilities, Increase Annual Transmission Service Revenue |  |  |  |  |  |  |  |  |  |  |  | 2,900,000pnm_PublicUtilitiesIncreaseAnnualTransmissionServiceRevenue / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember | 2,800,000pnm_PublicUtilitiesIncreaseAnnualTransmissionServiceRevenue / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember | 2,900,000pnm_PublicUtilitiesIncreaseAnnualTransmissionServiceRevenue / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember | 2,500,000pnm_PublicUtilitiesIncreaseAnnualTransmissionServiceRevenue / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember |  |  |  |  |  |  |
Texas-New Mexico Power Company [Member] | Subsequent Event [Member] | Advanced Meter System Deployment and Surcharge Request [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current number of customers that have elected non-standard meter service |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 89pnm_Currentnumberofcustomersthathaveelectednonstandardmeterservice / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_AdvancedMeterSystemDeploymentAndSurchargeRequestMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember |
Texas-New Mexico Power Company [Member] | Subsequent Event [Member] | Energy Efficiency [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Approved Program Implementation Costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5,700,000pnm_PublicUtilitiesApprovedProgramImplementationCosts / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_EnergyEfficiencyMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember |  |  |  |  |  |
Texas-New Mexico Power Company [Member] | Subsequent Event [Member] | Transmission Cost of Service Rates [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 27,100,000us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 25,200,000us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember |  |  |  |
Public Utilities, Increase Annual Transmission Service Revenue |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,200,000pnm_PublicUtilitiesIncreaseAnnualTransmissionServiceRevenue / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember |  |  |  |
Public Utilities, Requested Increase Annual Transmission Service Revenue |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,400,000pnm_PublicUtilitiesRequestedIncreaseAnnualTransmissionServiceRevenue / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember / pnm_ScheduleOfRegulatoryRateMattersAxis = pnm_TransmissionCostOfServiceRatesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember |  |  |  |  |
Four Corners [Member] | Public Service Company of New Mexico [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Jointly Owned Utility Plant Proportionate Ownership Share, Other Entities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7.00%pnm_JointlyOwnedUtilityPlantProportionateOwnershipShareOtherEntities / us-gaap_JointlyOwnedUtilityPlantAxis = pnm_FourCornersMember / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Period of time to file a waiver of rights of first refusal |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 120 days |  |  |

X
- Definition Current number of customers that have elected non-standard meter service + References No definition available. + Details
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- Definition Jointly Owned Utility Plant Proportionate Ownership Share, Other Entities + References No definition available. + Details
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- Definition Period of time to file a waiver of rights of first refusal + References No definition available. + Details
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- Definition Presumed number of customers that will elect non-standard meter service + References No definition available. + Details
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- Definition Public Utilites, Additional Renewable Procurements Spending Required by NMPRC + References No definition available. + Details
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- Definition Public Utilities, Actual cost per MWh for additional necessary procurements to comply with RPS + References No definition available. + Details
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- Definition Public Utilities, Additional Transmission Costs Requested + References No definition available. + Details
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Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Public Utilities, Annual Revenue To be Collected Under 2015 Rider Rate + References No definition available. + Details
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Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
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- Definition Public Utilities, Anticipated future profit incentive 2015 + References No definition available. + Details
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- Definition Public Utilities, Anticipated future profit incentive 2016 + References No definition available. + Details
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- Definition Public Utilities, Approved additional rate increase, Amount + References No definition available. + Details
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- Definition Public Utilities, Approved Additional Transmission Costs + References No definition available. + Details
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Namespace Prefix: | pnm_
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- Definition Public Utilities, Approved cost per MWh for additional necessary procurements to comply with RPS + References No definition available. + Details
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- Definition Public Utilities, Approved Deployment Costs + References No definition available. + Details
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- Definition Public Utilities, Approved Profit Incentive Adder Revenues Related To Energy Efficiency Program + References No definition available. + Details
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- Definition Public Utilities, Approved Profit Incentive Adder Revenues Related To Energy Efficiency Program, Percentage of Program Costs + References No definition available. + Details
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- Definition Public Utilities, Approved Program Implementation Costs + References No definition available. + Details
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- Definition Public Utilities, Approved Program Implementation Costs, Bonus + References No definition available. + Details
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- Definition Public Utilities, Approved Revised cost per MWh for additional necessary procurements to comply with RPS + References No definition available. + Details
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- Definition Public Utilities, Average customer bill increase percentage + References No definition available. + Details
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- Definition Public Utilities, Collection of Deployment Costs Through Surcharge Period + References No definition available. + Details
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- Definition Public Utilities, Completion Period of Advanced Meter Deployment + References No definition available. + Details
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- Definition Public Utilities, Energy Efficiency Incentive adder collected + References No definition available. + Details
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- Definition Public Utilities, Estimated Cost of Mega Watts of Solar Photovoltaic Capacity + References No definition available. + Details
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- Definition Public Utilities, Final Cost of Solar Photovoltaic Capacity + References No definition available. + Details
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- Definition Public Utilities, First Year Cost of Wind Capacity Planned Purchase Agreement + References No definition available. + Details
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- Definition Public Utilities, Fuel Costs to be Collected + References No definition available. + Details
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- Definition Public Utilities, Future Required Percentage of Diversification + References No definition available. + Details
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- Definition Public Utilities, Increase Annual Transmission Service Revenue + References No definition available. + Details
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- Definition Public Utilities, Lease ownership percentage in EIP + References No definition available. + Details
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- Definition Public Utilities, Non-standard metering ongoing expenses monthly charge + References No definition available. + Details
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- Definition Public Utilities, Non-standard metering ongoing expenses, Proposed monthly charge + References No definition available. + Details
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- Definition Public Utilities, Non-standard metering, Proposed ongoing expenses total to be borne by opt-out customers + References No definition available. + Details
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- Definition Public Utilities, Non-standard metering service cost initial fee range + References No definition available. + Details
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- Definition Public Utilities, Non-standard metering service cost, Proposed initial fee range + References No definition available. + Details
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- Definition Public Utilities, Non-standard metering service, Proposed cost total to be borne by opt-out customers + References No definition available. + Details
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- Definition Public Utilities, Number of MegaWatt Hours of renewable resources + References No definition available. + Details
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- Definition Public Utilities, Number of Mega Watts of Solar Photovoltaic Capacity + References No definition available. + Details
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- Definition Public Utilities, Number of Mega Watts of Solar Photovoltaic Capacity, Current Output + References No definition available. + Details
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- Definition Public Utilities, Number of Mega Watts of Solar Photovoltaic Capacity, Expected Output + References No definition available. + Details
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- Definition Public Utilities, Number of Mega Watts of Wind Energy Capacity + References No definition available. + Details
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- Definition Public Utilities, Percentage of requested rate increase pertaining to infrastructure investments + References No definition available. + Details
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- Definition Public Utilities, Program Costs Related To Energy Efficiency + References No definition available. + Details
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- Definition Public Utilities, Proposed Profit Incentive Adder Revenues Related To Energy Efficiency Program + References No definition available. + Details
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- Definition Public Utilities, Rate Rider Estimated Incentives Under-Recovery + References No definition available. + Details
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- Definition Public Utilities, Rate Rider Program Costs Over-Recovery + References No definition available. + Details
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- Definition Reasonable Cost Threshold + References No definition available. + Details
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- Definition Public Utilities, Requested Increase Annual Transmission Service Revenue + References No definition available. + Details
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- Definition Regulated Operations, Required Percentage of Diversification + References No definition available. + Details
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- Definition Regulated Operations, Required Percentage of Renewable Energy in Portfolio to Electric Sales + References No definition available. + Details
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- Definition Public Utilities, Resettlement award of previously remanded rates + References No definition available. + Details
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- Definition Public Utilities, Retention Percentage of Sales Margins + References No definition available. + Details
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- Definition Public Utilities, Revenue For Power Sold Under Specific Contract + References No definition available. + Details
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- Definition Public Utilities, Revenue from Renewable energy rider + References No definition available. + Details
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- Definition Public Utilities, Rider Condition of Earned Return on Jurisdictional Equity in 2013 + References No definition available. + Details
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- Definition Public Utilities, Unapproved 2015 Program Implementation Costs + References No definition available. + Details
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- Definition Public Utilities, Under-collected balance write-off + References No definition available. + Details
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- Definition Public Utilities, Wind Capacity Planned Purchase Agreement Term + References No definition available. + Details
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- Definition Amount of public utility's approved rate increase (decrease) by regulatory agency. + References No definition available. + Details
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