XML 81 R58.htm IDEA: XBRL DOCUMENT
v3.19.1

Commitments and Contingencies - The Clean Air Act (Details) $ in Millions | 3 Months Ended |  |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 31, 2019 USD ($) option T | Feb. 25, 2019 parts_per_billion | Dec. 31, 2018 USD ($) MW | Feb. 09, 2016 state | Oct. 01, 2015 parts_per_billion | Sep. 30, 2015 parts_per_billion | May 14, 2015 lb / MMBTU | Apr. 30, 2013 well | Feb. 28, 2013 claim state mine | Dec. 31, 1999 state
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Number of options for meeting BTA standards | option | 7 |  |  |  |  |  |  |  |  |
Expected number of additional monitoring wells | 38 |  |  |  |  |  |  |  |  |
Clean Air Act related to regional haze |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Number of states to address regional haze (in states) | state |  |  |  |  |  |  |  |  |  | 50
Potential to emit tons per year of visibility impairing pollution (in tons, more than) | T | 250 |  |  |  |  |  |  |  |  |
Clean Power Plan |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Number of states that filed a petition against the Clean Power Plan | state |  |  |  | 29 |  |  |  |  |  |
PNM | WEG v OSM lawsuit |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Number of mines impacted | mine |  |  |  |  |  |  |  |  | 7 |
Number of states impacted | state |  |  |  |  |  |  |  |  | 4 |
Number of claims for relief, filed | claim |  |  |  |  |  |  |  |  | 15 |
PNM | Santa Fe generating station |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Number of wells with elevated levels of nitrates | well |  |  |  |  |  |  |  | 3 |  |
PNM | San Juan Generating Station Unit 4 | Clean Air Act, SNCR |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Pre-tax impairment of investments |  |  | $ 35.0 |  |  |  |  |  |  |
Undepreciated investment in ownership to be obtained |  |  | 11.9 |  |  |  |  |  |  |
Forecasted undepreciated investment |  |  | $ 23.1 |  |  |  |  |  |  |
Remaining undepreciated investment | $ 371.6 |  |  |  |  |  |  |  |  |
PNM | San Juan Generating Station | Clean Air Act, SNCR |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Additional ownership to be obtained (in megawatts) | MW |  |  | 132 |  |  |  |  |  |  |
PNM | San Juan Generating Station | WEG v OSM lawsuit |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Number of claims for relief, filed | claim |  |  |  |  |  |  |  |  | 2 |
PNMR Development | San Juan Generating Station Unit 4 | Clean Air Act, SNCR |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Potential acquisition of ownership (in megawatts) | MW |  |  | 65 |  |  |  |  |  |  |
Maximum | PNM | San Juan Generating Station and Four Corners |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Government standard emission limit (in ozone parts per million) | parts_per_billion |  | 75 |  |  | 70 | 75 |  |  |  |
San Juan Generating Station | PNM | National Ambient Air Quality Standards |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |
Revised SO2 emissions (in pounds per MMBTU) | lb / MMBTU |  |  |  |  |  |  | 0.10 |  |  |

X
- Definition Expected Number Of Additional Monitoring Wells + References No definition available. + Details
Name: | pnm_ExpectedNumberOfAdditionalMonitoringWells
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number Of Options For Meeting BTA Standards + References No definition available. + Details
Name: | pnm_NumberOfOptionsForMeetingBTAStandards
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of claims for relief, filed + References No definition available. + Details
Name: | pnm_Numberofclaimsforrelieffiled
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of mines impacted + References No definition available. + Details
Name: | pnm_Numberofminesimpacted
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of states impacted + References No definition available. + Details
Name: | pnm_Numberofstatesimpacted
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of states that filed a petition against the Clean Power Plan + References No definition available. + Details
Name: | pnm_NumberofstatesthatfiledapetitionagainsttheCleanPowerPlan
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of wells with elevated levels of nitrates + References No definition available. + Details
Name: | pnm_Numberofwellswithelevatedlevelsofnitrates
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Additional Ownership To Be Obtained, in Megawatts + References No definition available. + Details
Name: | pnm_PublicUtilitiesAdditionalOwnershipToBeObtainedinMegawatts
Namespace Prefix: | pnm_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Commitments And Contingencies [Line Items] + References No definition available. + Details
Name: | pnm_PublicUtilitiesCommitmentsAndContingenciesLineItems
Namespace Prefix: | pnm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, Government Standard Emission Limit + References No definition available. + Details
Name: | pnm_PublicUtilitiesGovernmentStandardEmissionLimit
Namespace Prefix: | pnm_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Number of States To Address Regional Haze + References No definition available. + Details
Name: | pnm_PublicUtilitiesNumberOfStatesToAddressRegionalHaze
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Potential Acquisition of Ownership in Megawatts + References No definition available. + Details
Name: | pnm_PublicUtilitiesPotentialAcquisitionofOwnershipinMegawatts
Namespace Prefix: | pnm_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Potential to emit tons per year of visibility impairing pollution, maximum + References No definition available. + Details
Name: | pnm_PublicUtilitiesPotentialtoemittonsperyearofvisibilityimpairingpollutionmaximum
Namespace Prefix: | pnm_
Data Type: | num:massItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Pre-Tax Impairment of Investments + References No definition available. + Details
Name: | pnm_PublicUtilitiesPreTaxImpairmentofInvestments
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Public Utilities, Remaining Undepreciated Investment + References No definition available. + Details
Name: | pnm_PublicUtilitiesRemainingUndepreciatedInvestment
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Public Utilities, Revised SO2 Emissions Agreed Upon + References No definition available. + Details
Name: | pnm_PublicUtilitiesRevisedSO2EmissionsAgreedUpon
Namespace Prefix: | pnm_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Undepreciated Investment In Ownership To Be Obtained + References No definition available. + Details
Name: | pnm_PublicUtilitiesUndepreciatedInvestmentInOwnershipToBeObtained
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Public Utilities, forecasted undepreciated investment + References No definition available. + Details
Name: | pnm_PublicUtilitiesforecastedundepreciatedinvestment
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_CleanAirActRelatedToRegionalHazeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_CleanPowerPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=pnm_PublicServiceCompanyOfNewMexicoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_WEGvOSMLawsuitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_SantaFegeneratingstationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_SanJuanGeneratingStationUnit4Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_CleanAirActSncrMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_SanJuanGeneratingStationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=pnm_PNMRDevelopmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_SanJuanGeneratingStationAndFourCornersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_JointlyOwnedGeneratingFacilitiesAxis=pnm_SanJuanGeneratingStationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_NationalAmbientAirQualityStandardsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |