XML 78 R58.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Commitments and Contingencies - The Clean Air Act (Details) $ in Millions |  | 9 Months Ended |  |  |  |  |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 02, 2015 lb / MMBTU T | Sep. 30, 2018 USD ($) lbsofnox / mmbtu option joint_owner T | May 29, 2018 parts_per_billion | Dec. 31, 2017 MW | Jan. 26, 2016 state | Dec. 31, 2015 MW | Oct. 01, 2015 parts_per_billion | Sep. 30, 2015 parts_per_billion | May 14, 2015 lb / MMBTU | Dec. 30, 2013 | Apr. 30, 2013 well | Feb. 28, 2013 lawsuit state mine | Aug. 06, 2012 compliance_alternative | Dec. 31, 1999 state
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Undepreciated investment in ownership to be obtained |  | $ 405.5 |  |  |  |  |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  |  |  |
San Juan Generating Station Unit 4 | Clean Air Act, SNCR |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of other joint owners | joint_owner |  | 8 |  |  |  |  |  |  |  |  |  |  |  |
PNM | National Ambient Air Quality Standards, 2015 EPA Legal Settlement |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period of time to act on settlement | 16 months |  |  |  |  |  |  |  |  |  |  |  |  |
Emissions tons of SO2 per year (more than) | T | 16,000 |  |  |  |  |  |  |  |  |  |  |  |  |
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 | lawsuit |  |  |  |  |  |  |  |  |  |  |  | 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 Hearing Examiner, Recommended Denial |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional ownership to be obtained (in megawatts) | MW |  |  |  |  |  | 132 |  |  |  |  |  |  |  |
Undepreciated interest in ownership to be obtained |  | $ 20.3 |  |  |  |  |  |  |  |  |  |  |  |
PNM | San Juan Generating Station Unit 4 | Clean Air Act, SNCR |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional ownership to be obtained (in megawatts) | MW |  |  |  |  |  | 65 |  |  |  |  |  |  |  |
Undepreciated interest in ownership to be obtained |  | $ 10.1 |  |  |  |  |  |  |  |  |  |  |  |
PNM | Palo Verde Nuclear Generating Station Unit 3 | Clean Air Act, SNCR |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of megawatts nuclear generation (in megawatts) | MW |  |  |  | 134 |  |  |  |  |  |  |  |  |  |
PNM | Four Corners | Clean Air Act related to post combustion controls |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of compliance alternatives | compliance_alternative |  |  |  |  |  |  |  |  |  |  |  |  | 2 |
Plant requirement to meet NOx emissions limit (in pounds of NOx per MMBTU) | lbsofnox / mmbtu |  | 0.015 |  |  |  |  |  |  |  |  |  |  |  |
Plant requirement to meet opacity limit |  | 20.00% |  |  |  |  |  |  |  |  |  |  |  |
Rule imposes opacity limitation on certain fugitive dust emissions from coal and material handling operations |  | 20.00% |  |  |  |  |  |  |  |  |  |  |  |
Estimate of possible loss |  | $ 88.6 |  |  |  |  |  |  |  |  |  |  |  |
PNM | Four Corners Units 4 and 5 (Coal) | Clean Air Act related to post combustion controls |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership percentage |  | 13.00% |  |  |  |  |  |  |  |  |  |  |  |
PNM | Four Corners Units 1, 2 and 3 (Coal) | Clean Air Act related to post combustion controls |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership percentage |  |  |  |  |  |  |  |  |  | 0.00% |  |  |  |
PNM | San Juan Generating Station | WEG v OSM lawsuit |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of claims for relief, filed | lawsuit |  |  |  |  |  |  |  |  |  |  |  | 2 |  |
Minimum | PNM | National Ambient Air Quality Standards, 2015 EPA Legal Settlement |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Emissions tons of SO2 per year (more than) | T | 2,600 |  |  |  |  |  |  |  |  |  |  |  |  |
One-hour SO2 emissions rate (in pounds per MMBTU) | lb / MMBTU | 0.45 |  |  |  |  |  |  |  |  |  |  |  |  |
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 Period of time to act on settlement + References No definition available. + Details
Name: | pnm_Periodoftimetoactonsettlement
Namespace Prefix: | pnm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, 1-hour SO2 Emissions Rate + References No definition available. + Details
Name: | pnm_PublicUtilities1hourSO2EmissionsRate
Namespace Prefix: | pnm_
Data Type: | xbrli:decimalItemType
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, Emissions Tons of SO2 per year + References No definition available. + Details
Name: | pnm_PublicUtilitiesEmissionsTonsofSO2peryear
Namespace Prefix: | pnm_
Data Type: | num:massItemType
Balance Type: | na
Period Type: | instant

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 Compliance alternatives + References No definition available. + Details
Name: | pnm_PublicUtilitiesNumberOfComplianceAlternatives
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
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, Number of Megawatts Nuclear Generation + References No definition available. + Details
Name: | pnm_PublicUtilitiesNumberofMegawattsNuclearGeneration
Namespace Prefix: | pnm_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Number of other owner + References No definition available. + Details
Name: | pnm_PublicUtilitiesNumberofotherowner
Namespace Prefix: | pnm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Ownership Percentage + References No definition available. + Details
Name: | pnm_PublicUtilitiesOwnershipPercentage
Namespace Prefix: | pnm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Plant Requirement to Meet NOx emissions Limit + References No definition available. + Details
Name: | pnm_PublicUtilitiesPlantRequirementtoMeetNOxemissionsLimit
Namespace Prefix: | pnm_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Plant Requirement to Meet Opacity Limit, Percentage + References No definition available. + Details
Name: | pnm_PublicUtilitiesPlantRequirementtoMeetOpacityLimitPercentage
Namespace Prefix: | pnm_
Data Type: | num:percentItemType
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, 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, Rule Imposes Opacity Limitation on Certain Fugitive Dust Emissions From Coal and Material Handling Operations + References No definition available. + Details
Name: | pnm_PublicUtilitiesRuleImposesOpacityLimitationOnCertainFugitiveDustEmissionsFromCoalAndMaterialHandlingOperations
Namespace Prefix: | pnm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Public Utilities, Undepreciated Interest In Ownership To Be Obtained + References No definition available. + Details
Name: | pnm_PublicUtilitiesUndepreciatedInterestInOwnershipToBeObtained
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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 Reflects the estimated amount of loss from the specified contingency as of the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=115931803&loc=d3e12021-110248 + Details
Name: | us-gaap_LossContingencyEstimateOfPossibleLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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: | 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: | dei_LegalEntityAxis=pnm_PublicServiceCompanyOfNewMexicoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_NationalAmbientAirQualityStandards2015EPALegalSettlementMember
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: | pnm_CommitmentsAndContingenciesRelatedToEnvironmentAndOtherNatureAxis=pnm_CleanAirActSNCRHearingExaminerRecommendedDenialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_PaloVerdeNuclearGeneratingStationUnit3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_FourCornersUnits4And5CoalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnm_FourCornersUnits12and3CoalMember
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: | srt_RangeAxis=srt_MinimumMember
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: |