XML 153 R122.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Regulatory and Rate Matters - Firm-Requirements Wholesale Customers (Details) - Public Service Company of New Mexico [Member] $ in Millions |  | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Dec. 06, 2012 USD ($) | Jun. 30, 2015 USD ($) | Jun. 30, 2014 USD ($) | Dec. 31, 2017 MW | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($)
Firm Requirements Wholesale Power Rate Case, Navopache [Member] [Member] |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Approved rate increase (decrease) | $ 5.3 |  |  |  |  |  |
Revenue for power sold under specific contract |  |  |  |  | $ 20.0 | $ 27.1 | $ 28.4
Firm Requirements Wholesale Power Rate Case, Navopache [Member] [Member] | Scenario, Forecast [Member] |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Serving megawatts of load under a lower tariff (in mw) | MW |  |  |  | 10 |  |  |
Firm Requirements Wholesale Power Rate Case [Member] |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Contract extension | 10 years |  |  |  |  |  |
Firm Requirements Wholesale Power Contract, Gallup [Member] |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Revenue for power sold under specific contract |  |  | $ 6.1 |  |  |  |
City of Gallup, New Mexico Contract [Member] |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Gain on sale of substation |  | $ 1.1 |  |  |  |  |

X
- Definition Public Utilities, Contract Extension + References No definition available. + Details
Name: | pnm_PublicUtilitiesContractExtension
Namespace Prefix: | pnm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, Expected average monthly usage in megawatts + References No definition available. + Details
Name: | pnm_PublicUtilitiesExpectedaveragemonthlyusageinmegawatts
Namespace Prefix: | pnm_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, Gain on sale of substation + References No definition available. + Details
Name: | pnm_PublicUtilitiesGainonsaleofsubstation
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Public Utilities, Revenue For Power Sold Under Specific Contract + References No definition available. + Details
Name: | pnm_PublicUtilitiesRevenueForPowerSoldUnderSpecificContract
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of public utility's approved rate increase (decrease) by regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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_PublicUtilitiesGeneralDisclosuresLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
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: | pnm_ScheduleOfRegulatoryRateMattersAxis=pnm_FirmRequirementsWholesalePowerRateCaseNavopacheMemberMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_ScheduleOfRegulatoryRateMattersAxis=pnm_FirmRequirementsWholesalePowerRateCaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_ScheduleOfRegulatoryRateMattersAxis=pnm_FirmRequirementsWholesalePowerContractGallupMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_ScheduleOfRegulatoryRateMattersAxis=pnm_CityOfGallupNewMexicoContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |