XML 70 R47.htm IDEA: XBRL DOCUMENT
v3.19.1

Fair Value of Derivative and Other Financial Instruments - Margin, Notional Amounts and Credit Rating (Details) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2019 USD ($) MMBTU MWh | Dec. 31, 2018 USD ($) MMBTU MWh
Derivative [Line Items] |  |
Contract in a liability position | $ | $ 0 | $ 0
PNM | Commodity derivatives | Fair value hedging | Buy |  |
Derivative [Line Items] |  |
Economic Hedges (in mmbtu and mwh) | MMBTU | 100,000 | 100,000
PNM | Commodity derivatives | Fair value hedging | Sell |  |
Derivative [Line Items] |  |
Economic Hedges (in mmbtu and mwh) | MWh | 400 | 0

X
- Definition Contract With Customer, Liability, Net + References No definition available. + Details
Name: | pnm_ContractWithCustomerLiabilityNet
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Nominal energy measure used to calculate payments on a derivative instrument. + References No definition available. + Details
Name: | us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure
Namespace Prefix: | us-gaap_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CommodityContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_FairValueHedgingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PositionAxis=us-gaap_LongMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PositionAxis=us-gaap_ShortMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |