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Income Taxes (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2015 | Mar. 31, 2014
Income Tax Contingency [Line Items] |  |
New Mexico Corporate tax rate, current | 7.60%pnm_NewMexicoCorporatetaxratecurrent |
New Mexico Corporate tax rate, 2014 | 5.90%pnm_NewMexicoCorporatetaxrateeffectiveby2018 |
Decrease in regulatory liabilities due to change in state corporate tax rate | $ 2.0 pnm_Decreaseinregulatoryliabilitiesduetochangeinstatecorporatetaxrate | $ 4.6 pnm_Decreaseinregulatoryliabilitiesduetochangeinstatecorporatetaxrate
Decrease in deferred tax asset due to change in state corporate tax rate |  | 0.2 pnm_Decreaseindeferredtaxassetduetochangeinstatecorporatetaxrate
State Net Operating Loss Carryforward, Impairment | 1.0 pnm_StateNetOperatingLossCarryforwardImpairment |
Public Service Company of New Mexico [Member] |  |
Income Tax Contingency [Line Items] |  |
Increase in deferred tax asset not related to regulatory activity, as a result of tax rate change | 0.7 pnm_Increaseindeferredtaxassetnotrelatedtoregulatoryactivityasaresultoftaxratechange / us-gaap_StatementBusinessSegmentsAxis = pnm_PublicServiceCompanyOfNewMexicoMember |
Decrease in income tax expense due to tax rate change | 0.5 pnm_Decreaseinincometaxexpenseduetotaxratechange / us-gaap_StatementBusinessSegmentsAxis = pnm_PublicServiceCompanyOfNewMexicoMember |
State Net Operating Loss Carryforward, Impairment | 0.7 pnm_StateNetOperatingLossCarryforwardImpairment / us-gaap_StatementBusinessSegmentsAxis = pnm_PublicServiceCompanyOfNewMexicoMember |
Corporate and Other [Member] |  |
Income Tax Contingency [Line Items] |  |
Decrease in income tax expense due to tax rate change | 0.2 pnm_Decreaseinincometaxexpenseduetotaxratechange / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
State Net Operating Loss Carryforward, Impairment | $ 0.3 pnm_StateNetOperatingLossCarryforwardImpairment / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |

X
- Definition Decrease in deferred tax asset due to change in state corporate tax rate + References No definition available. + Details
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- Definition Decrease in income tax expense due to tax rate change + References No definition available. + Details
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- Definition Decrease in regulatory liabilities due to change in state corporate tax rate + References No definition available. + Details
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Namespace Prefix: | pnm_
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Balance Type: | debit
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- Definition Increase in deferred tax asset not related to regulatory activity, as a result of tax rate change + References No definition available. + Details
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- Definition New Mexico Corporate tax rate, current + References No definition available. + Details
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- Definition New Mexico Corporate tax rate, effective by 2018 + References No definition available. + Details
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- Definition State Net Operating Loss Carryforward, Impairment + References No definition available. + Details
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- Details
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- Details
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Namespace Prefix: |
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Period Type: |

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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |