Defined Benefit Plan, Actuarial Gain (Loss) resulting from changes in demographics and other trends

No definition available.

Name:	pnm_DefinedBenefitPlanActuarialGainLossresultingfromchangesindemographicsandothertrends
Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Defined Benefit Plan, Actuarial Gain (Loss) resulting from changes in other assumptions and experience

+ References

No definition available.

+ Details

Name:	pnm_DefinedBenefitPlanActuarialGainLossresultingfromchangesinotherassumptionsandexperience
Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation Related To Anticipated Contributions, Weighted Average Discount Rate

+ References

No definition available.

+ Details

Name:	pnm_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRelatedToAnticipatedContributionsWeightedAverageDiscountRate
Namespace Prefix:	pnm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets Decrease Resulting in Increase Net Periodic Costs In Next Fiscal Year

+ References

No definition available.

+ Details

Name:	pnm_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssetsDecreaseResultingInIncreaseNetPeriodicCostsInNextFiscalYear
Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return Resulting from Effect of One-Percentage Point Decrease

+ References

No definition available.

+ Details

Name:	pnm_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnResultingFromEffectOfOnePercentagePointDecrease
Namespace Prefix:	pnm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return Resulting from Effect of One-Percentage Point Increase

+ References

No definition available.

+ Details

Name:	pnm_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnResultingFromEffectOfOnePercentagePointIncrease
Namespace Prefix:	pnm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Benefit Plan, Estimated Future Employer Contributions in Year Two Through Year Five

+ References

No definition available.

+ Details

Name:	pnm_DefinedBenefitPlanEstimatedFutureEmployerContributionsinYearTwoThroughYearFive
Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Defined Benefit Plan, Estimated Future Employer Contributions in Year Two Through Year Four

+ References

No definition available.

+ Details

Name:	pnm_DefinedBenefitPlanEstimatedFutureEmployerContributionsInYearTwoThroughYearFour
Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Defined Benefit Plans, Gains and losses that lie outside the corridor, amortized in years

+ References

No definition available.

+ Details

Name:	pnm_DefinedBenefitPlansGainsAndLossesThatLieOutsideCorridorAmortizedInYears
Namespace Prefix:	pnm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined Contribution Plan, non matching contribution of eligible compensation based on eligible employee's age

+ References

No definition available.

+ Details

Name:	pnm_DefinedContributionPlanNonMatchingContributionOfEligibleCompensationBasedOnEligibleEmployeesAge
Namespace Prefix:	pnm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates, Net periodic expense and APBO

+ References

No definition available.

+ Details

Name:	pnm_EffectofOnePercentagePointChangeinAssumedHealthCareCostTrendRatesNetperiodicexpenseandAPBO
Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount before tax, after reclassification adjustments, of prior service cost (credit) that has not been recognized in the income statement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (j)

-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580

+ Details

Name:	us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Long-Term Rate of Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512013

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(3)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The increase in the fair value of plan assets from contributions made by the employer.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Changes in the defined benefit obligation, not otherwise separately disclosed in the financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanOtherChanges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Target allocation of investments of this type to total plan assets presented on a weighted average basis.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (d)(i)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (c)(i)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e2446-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e2446-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (d)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount before tax of (increase) decrease in the value of the projected benefit obligation related to a change in an actuarial assumption and increase (decrease) in the value of the plan assets resulting from experience different from that assumed, that has not been recognized in net periodic benefit (cost) credit.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (j)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(4)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=pnm_PNMandTNMPDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=pnm_PublicServiceCompanyOfNewMexicoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=pnm_TexasNewMexicoPowerCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	invest_InvestmentGeographicRegionAxis=pnm_DevelopedCountriesOutsideOfUnitedStatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	pnm_ChangeinassumptionsAxis=pnm_RevisedMortalityTablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=pnm_AlternativeInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Pension and Other Postretirement Benefits Narrative (Details) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	4.00%
Defined Benefit Plans, Gains and losses that lie outside the corridor, amortized (in years)	5 years
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	75.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected long-term return resulting from effect of one-percentage point decrease (as a percent)	1.00%
Expected long-term return resulting from effect of one-percentage point increase (as a percent)	1.00%
Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected long-term return resulting from effect of one-percentage point decrease (as a percent)	1.00%
Public Service Company of New Mexico [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	7.20%	7.65%	8.25%
Defined Benefit Plan, Other Changes	50,600,000	$ (60,900,000)
Defined Benefit Plan, Actuarial Gain (Loss) resulting from changes in demographics and other trends	(200,000)	(4,400,000)
Defined Benefit Plan, Actuarial Gain (Loss) resulting from changes in other assumptions and experience	200,000	100,000
Actual plan asset allocations (as a percent)	14.30%
Expected Long-term return on assets decrease resulting in increase net periodic costs In next fiscal year	5,800,000
Employer contributions	0	60,000,000
Estimated future employer contributions from 2013-2017	22,000,000
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	(34,345,000)
Public Service Company of New Mexico [Member] \| Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	8.50%	8.50%	8.50%
Defined Benefit Plan, Other Changes	6,700,000	(8,800,000)
Defined Benefit Plan, Actuarial Gain (Loss) resulting from changes in demographics and other trends	5,400,000	(4,200,000)
Actual plan asset allocations (as a percent)	10.20%
Expected Long-term return on assets decrease resulting in increase net periodic costs In next fiscal year	700,000
Employer contributions	3,532,000	3,576,000
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	(2,800,000)
Estimated future employer contributions in next fiscal year	3,500,000
Defined Benefit Plan, Estimated Future Employer Contributions in Year Two Through Year Five	14,000,000
Texas-New Mexico Power Company [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	7.20%	7.65%	8.25%
Defined Benefit Plan, Other Changes	5,100,000	(6,400,000)
Defined Benefit Plan, Actuarial Gain (Loss) resulting from changes in demographics and other trends	400,000	1,400,000
Defined Benefit Plan, Actuarial Gain (Loss) resulting from changes in other assumptions and experience	(1,300,000)	(100,000)
Actual plan asset allocations (as a percent)	13.50%
Expected Long-term return on assets decrease resulting in increase net periodic costs In next fiscal year	600,000
Employer contributions	0	1,000,000
Estimated future employer contributions from 2013-2017	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	(4,420,000)
Texas-New Mexico Power Company [Member] \| Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	6.50%	6.50%	6.50%
Defined Benefit Plan, Other Changes	1,100,000	(1,300,000)
Defined Benefit Plan, Actuarial Gain (Loss) resulting from changes in demographics and other trends	(100,000)	(200,000)
Actual plan asset allocations (as a percent)	8.90%
Expected Long-term return on assets decrease resulting in increase net periodic costs In next fiscal year	100,000
Employer contributions	343,000	342,000
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	(1,300,000)
Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates, Net periodic expense and APBO	0
Estimated future employer contributions in next fiscal year	300,000
Defined Benefit Plan, Estimated Future Employer Contributions in Year Two Through Year Five	1,400,000
PNM and TNMP [Domain] \| Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Prior Service Cost (Credit), before Tax	0
Equity Securities [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations (as a percent)	21.00%
Equity Securities [Member] \| Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations (as a percent)	70.00%
Debt Securities [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations (as a percent)	65.00%
Debt Securities [Member] \| Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations (as a percent)	30.00%
Alternative Investments [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations (as a percent)	14.00%
Minimum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Contribution Plan, non matching contribution of eligible compensation based on eligible employee's age	3.00%
Minimum [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average discount rate related to anticipated contributions (as a percent)	4.80%
Maximum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Contribution Plan, non matching contribution of eligible compensation based on eligible employee's age	10.00%
Maximum [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average discount rate related to anticipated contributions (as a percent)	5.50%
Developed Countries Outside of United States [Member] \| Equity Securities [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations (as a percent)	6.00%
Revised Mortality Tables [Member] \| Public Service Company of New Mexico [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Other Changes	21,900,000
Revised Mortality Tables [Member] \| Public Service Company of New Mexico [Member] \| Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Other Changes	3,200,000
Revised Mortality Tables [Member] \| Texas-New Mexico Power Company [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Other Changes	2,500,000
Revised Mortality Tables [Member] \| Texas-New Mexico Power Company [Member] \| Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Other Changes	500,000
Revised Mortality Tables [Member] \| Subsequent Event [Member] \| Public Service Company of New Mexico [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions				$ 30,000,000