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Income Taxes Interest Expense (Income) Related to Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Interest income related to income taxes	$ 146us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense	$ 242us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense	$ 243us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense
Public Service Company of New Mexico [Member]
Income Taxes [Line Items]
Interest income related to income taxes	148us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	251us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember	244us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense / dei_LegalEntityAxis = pnm_PublicServiceCompanyOfNewMexicoMember
Texas-New Mexico Power Company [Member]
Income Taxes [Line Items]
Interest income related to income taxes	$ (2)us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	$ (2)us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember	$ (3)us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense / dei_LegalEntityAxis = pnm_TexasNewMexicoPowerCompanyMember

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- Definition

Amount of interest expense for an underpayment of income taxes.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

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