XML 75 R48.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Stock-Based Compensation (Details) - USD ($) |  | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 03, 2017 | Sep. 30, 2017 | Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2016 | Feb. 28, 2017 | Dec. 31, 2015 | Mar. 31, 2015 | Jan. 01, 2015 | Mar. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of shares granted (in shares) |  |  | 0 |  |  |  |  |  |  |
Vesting period |  |  | 1 year |  |  |  |  |  |  |
Unrecognized expense related to stock awards |  | $ 4,800,000 | $ 4,800,000 |  | $ 4,500,000 |  |  |  |  |
Excess tax benefits |  | $ 200,000 | $ 2,300,000 |  |  |  |  |  |  |
Cumulative effect adjustment |  |  |  |  | $ 10,382,000 |  |  |  |  |
Restricted Stock, Shares |  |  |  |  |  |  |  |  |  |
Expired (in shares) |  |  | (3,000) |  |  |  |  |  |  |
Restricted Stock, Weighted- Average Grant Date Fair Value |  |  |  |  |  |  |  |  |  |
Expired (in dollars per share) |  |  | $ 30.50 |  |  |  |  |  |  |
Stock Options, Shares |  |  |  |  |  |  |  |  |  |
Outstanding at beginning of period (in shares) |  |  | 305,874 |  |  |  |  |  |  |
Granted (in shares) |  |  | 0 |  |  |  |  |  |  |
Exercised (in shares) |  |  | (109,433) |  |  |  |  |  |  |
Forfeited (in shares) |  |  | 0 |  |  |  |  |  |  |
Expired (in shares) |  |  | (3,000) |  |  |  |  |  |  |
Outstanding at end of period (in shares) |  | 193,441 | 193,441 |  | 305,874 |  |  |  |  |
Stock Options, Weighted- Average Exercise Price |  |  |  |  |  |  |  |  |  |
Outstanding at beginning of period (in dollars per share) |  |  | $ 12.29 |  |  |  |  |  |  |
Granted (in dollars per share) |  |  | 0.00 |  |  |  |  |  |  |
Exercised (in dollars per share) |  |  | 15.89 |  |  |  |  |  |  |
Forfeited (in dollars per share) |  |  | 0.00 |  |  |  |  |  |  |
Expired (in dollars per share) |  |  | 30.50 |  |  |  |  |  |  |
Outstanding at end of period (in dollars per share) |  | $ 9.98 | 9.98 |  | $ 12.29 |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] |  |  |  |  |  |  |  |  |  |
Weighted-average grant date fair value of options granted (in dollars per share) |  |  | $ 0.00 | $ 0.00 |  |  |  |  |  |
Total fair value of options that vested |  |  | $ 0 | $ 0 |  |  |  |  |  |
Total intrinsic value of options exercised |  |  | 2,234,000 | $ 1,208,000 |  |  |  |  |  |
Chairman, President, and Chief Executive Officer | Common stock | Achieves a specified improvement in total shareholder return at the end of 2016 compared to 2011 and she remains an employee |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Shares received if achieves specified improvement in total shareholders return (in shares) |  |  |  |  |  |  |  |  |  | 135,000
Chairman, President, and Chief Executive Officer | Common stock | Achieves specified improvement in total shareholder return at end of 2014 compared to 2011 and she remains employee |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Shares received if achieves specified improvement in total shareholders return (in shares) |  |  |  |  |  |  | 35,000 |  |  |
Chairman, President, and Chief Executive Officer | Common stock | Achieves specified improvement In total shareholder return at end of 2015 compared to 2011 and she remains employee |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Shares received if achieves specified improvement in total shareholders return (in shares) |  |  |  |  |  | 100,000 |  |  |  |
Chairman, President, and Chief Executive Officer | Common stock | Achieves a specific performance target by the end of 2019 and she remains an employee |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Shares received if achieves specified improvement in total shareholders return (in shares) |  |  |  |  |  |  |  | 53,859 |  |
Chairman, President, and Chief Executive Officer | Common stock | Achieves a specific performance target by the end of 2017 and she remains an employee |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Shares received if achieves specified improvement in total shareholders return (in shares) |  |  |  |  |  |  |  | 17,953 |  |
Executive Vice President and Chief Financial Officer | Common stock | Achieved performance target for 2015 and 2016 |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Share-based compensation arrangement by share-based payment award, purchase price of common stock |  |  |  |  |  |  |  |  | $ 100,000 |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant |  |  |  |  |  | 100,000 |  |  |  |
Restricted Stock, Shares |  |  |  |  |  |  |  |  |  |
Granted (in shares) | 2,754 |  |  |  |  |  |  |  |  |
Restricted Stock, Weighted- Average Grant Date Fair Value |  |  |  |  |  |  |  |  |  |
Granted (in dollars per share) | $ 36.30 |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] |  |  |  |  |  |  |  |  |  |
Weighted-average grant date fair value (in dollars per share) | $ 36.30 |  |  |  |  |  |  |  |  |
Executive Vice President and Chief Financial Officer | Common stock | Achieved performance target for 2015, 2016 and 2017 |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Share-based compensation arrangement by share-based payment award, purchase price of common stock |  |  |  |  |  |  |  |  | $ 275,000 |
Retained Earnings |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Cumulative effect adjustment |  |  |  |  | $ 10,382,000 |  |  |  |  |
Accounting Standards Update 2016-09 |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Accumulated deferred income taxes |  |  |  |  | (10,400,000) |  |  |  |  |
Accounting Standards Update 2016-09 | Retained Earnings |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Cumulative effect adjustment |  |  |  |  | $ 10,400,000 |  |  |  |  |
PNM |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Excess tax benefits |  | $ 100,000 | 1,700,000 |  |  |  |  |  |  |
TNMP |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Excess tax benefits |  | $ 100,000 | $ 600,000 |  |  |  |  |  |  |
Restricted Shares and Performance Based Shares |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Period of time stock expense is expected to be recognized |  |  | 2 years |  | 1 year 9 months 26 days |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] |  |  |  |  |  |  |  |  |  |
Expected quarterly dividends per share (in dollars per share) |  |  | $ 0.2425 | $ 0.2200 |  |  |  |  |  |
Risk-free interest rate |  |  | 1.50% | 0.94% |  |  |  |  |  |
Restricted Stock |  |  |  |  |  |  |  |  |  |
Restricted Stock, Shares |  |  |  |  |  |  |  |  |  |
Outstanding at beginning of period (in shares) |  |  | 218,316 |  |  |  |  |  |  |
Granted (in shares) |  |  | 248,271 |  |  |  |  |  |  |
Exercised (in shares) |  |  | (270,855) |  |  |  |  |  |  |
Forfeited (in shares) |  |  | (4,012) |  |  |  |  |  |  |
Expired (in shares) |  |  | 0 |  |  |  |  |  |  |
Outstanding at end of period (in shares) |  | 191,720 | 191,720 |  | 218,316 |  |  |  |  |
Restricted Stock, Weighted- Average Grant Date Fair Value |  |  |  |  |  |  |  |  |  |
Outstanding at beginning of period (in dollars per share) |  |  | $ 27.59 |  |  |  |  |  |  |
Granted (in dollars per share) |  |  | 23.06 | $ 26.49 |  |  |  |  |  |
Exercised (in dollars per share) |  |  | 20.92 |  |  |  |  |  |  |
Forfeited (in dollars per share) |  |  | 29.96 |  |  |  |  |  |  |
Expired (in dollars per share) |  |  | 0.00 |  |  |  |  |  |  |
Outstanding at end of period (in dollars per share) |  | $ 31.10 | $ 31.10 |  | $ 27.59 |  |  |  |  |
Stock Options, Shares |  |  |  |  |  |  |  |  |  |
Expired (in shares) |  |  | 0 |  |  |  |  |  |  |
Stock Options, Weighted- Average Exercise Price |  |  |  |  |  |  |  |  |  |
Expired (in dollars per share) |  |  | $ 0.00 |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] |  |  |  |  |  |  |  |  |  |
Weighted-average grant date fair value (in dollars per share) |  |  | $ 23.06 | $ 26.49 |  |  |  |  |  |
Total fair value of restricted shares that vested |  |  | $ 5,666,000 | $ 5,011,000 |  |  |  |  |  |
Performance Shares | Executive |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Shares granted (in shares) |  | 49,682 | 49,682 |  |  |  |  |  |  |
Shares exercised (in shares) |  | 49,682 | 49,682 |  |  |  |  |  |  |
Weighted percentage assigned to achieving market targets |  | 60.00% | 60.00% |  |  |  |  |  |  |
Weighted percentage assigned to achieving performance targets |  | 40.00% | 40.00% |  |  |  |  |  |  |
Maximum number of shares awarded in year 1 (in shares) |  | 163,712 | 163,712 |  |  |  |  |  |  |
Maximum number of shares awarded in year 2 (in shares) |  | 137,036 | 137,036 |  |  |  |  |  |  |
Maximum number of shares awarded in year 3 (in shares) |  | 133,632 | 133,632 |  |  |  |  |  |  |
Performance period |  |  | 3 years |  |  |  |  |  |  |
Market-Based Shares |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] |  |  |  |  |  |  |  |  |  |
Risk-free interest rate |  |  | 1.54% | 0.97% |  |  |  |  |  |
Dividend yield |  |  | 2.67% | 2.74% |  |  |  |  |  |
Expected volatility |  |  | 20.80% | 20.44% |  |  |  |  |  |
Stock options |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Aggregate intrinsic value of stock options outstanding |  | $ 5,900,000 | $ 5,900,000 |  |  |  |  |  |  |
Weighted-average remaining contract life |  |  | 1 year 9 months 18 days |  |  |  |  |  |  |
Number of outstanding stock options with an exercise price greater than the closing price (in shares) |  | 0 | 0 |  |  |  |  |  |  |
Performance Equity Plan |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Vesting period |  |  | 3 years |  |  |  |  |  |  |
Vesting rate |  |  | 100.00% |  |  |  |  |  |  |

X
- Definition Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount + References No definition available. + Details
Name: | pnm_EffectiveIncomeTaxRateReconciliationSharebasedCompensationExcessTaxBenefitAmount
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Performance period + References No definition available. + Details
Name: | pnm_Performanceperiod
Namespace Prefix: | pnm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share Based Compensation Arrangement by Share Based Payment Award Fair Value Assumptions Expected Quarterly Dividend Rate + References No definition available. + Details
Name: | pnm_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedQuarterlyDividendRate
Namespace Prefix: | pnm_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares in Year One + References No definition available. + Details
Name: | pnm_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesInYearOne
Namespace Prefix: | pnm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares in Year Three + References No definition available. + Details
Name: | pnm_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesInYearThree
Namespace Prefix: | pnm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares in Year Two + References No definition available. + Details
Name: | pnm_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesInYearTwo
Namespace Prefix: | pnm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share Based Compensation Arrangement by Share Based Payment Award Options Outstanding Shares Above Entities Stock Price + References No definition available. + Details
Name: | pnm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingSharesAboveEntitiesStockPrice
Namespace Prefix: | pnm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share Based Compensation Arrangement by Share Based Payment Award Options Vested in Period Total Fair Value + References No definition available. + Details
Name: | pnm_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriodTotalFairValue
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Share-based Compensation Arrangement by Share-based Payment Award, Vesting Rate + References No definition available. + Details
Name: | pnm_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingRate
Namespace Prefix: | pnm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share-based Compensation Arrangement by Share-based Payment Award, Previously Awarded Restricted Stock Exercised, Included in Shares Outstanding, Number + References No definition available. + Details
Name: | pnm_SharebasedCompensationArrangementbySharebasedPaymentAwardPreviouslyAwardedRestrictedStockExercisedIncludedinSharesOutstandingNumber
Namespace Prefix: | pnm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share-based Compensation Arrangement by Share-based Payment Award, Previously Awarded Restricted Stock Granted, Included in Shares Outstanding, Number + References No definition available. + Details
Name: | pnm_SharebasedCompensationArrangementbySharebasedPaymentAwardPreviouslyAwardedRestrictedStockGrantedIncludedinSharesOutstandingNumber
Namespace Prefix: | pnm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share based Compensation, weighted percentage assigned to achieving market targets + References No definition available. + Details
Name: | pnm_SharebasedCompensationweightedpercentageassignedtoachievingmarkettargets
Namespace Prefix: | pnm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share based Compensation, weighted percentage assigned to achieving performance targets + References No definition available. + Details
Name: | pnm_SharebasedCompensationweightedpercentageassignedtoachievingperformancetargets
Namespace Prefix: | pnm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share-based compensation arrangement by share-based payment award, Purchase price of common stock + References No definition available. + Details
Name: | pnm_SharebasedcompensationarrangementbysharebasedpaymentawardPurchasepriceofcommonstock
Namespace Prefix: | pnm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption. + References No definition available. + Details
Name: | us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences with jurisdictional netting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=84176650&loc=d3e31931-109318 + Details
Name: | us-gaap_DeferredIncomeTaxLiabilitiesNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(3) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(ii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iv) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
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_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(4) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Net number of share options (or share units) granted during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Gross number of share options (or share units) granted during the period. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average price at which option holders acquired shares when converting their stock options into shares. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of share options (or share units) exercised during the current period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_TitleOfIndividualAxis=pnm_ChairmanPresidentAndChiefExecutiveOfficerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_CommonStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_AchievedSpecifiedImprovementInTotalShareholderReturnTimeFrameAxis=pnm_AchievesSpecifiedImprovementInTotalShareholderReturnAtEndOf2016ComparedTo2011AndSheRemainsEmployeeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_AchievedSpecifiedImprovementInTotalShareholderReturnTimeFrameAxis=pnm_AchievesSpecifiedImprovementInTotalShareholderReturnAtEndOf2014ComparedTo2011AndSheRemainsEmployeeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_AchievedSpecifiedImprovementInTotalShareholderReturnTimeFrameAxis=pnm_AchievesSpecifiedImprovementInTotalShareholderReturnAtEndOf2015ComparedTo2011AndSheRemainsEmployeeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_AchievedSpecifiedImprovementInTotalShareholderReturnTimeFrameAxis=pnm_Achievesaspecificperformancetargetbytheendof2019andsheremainsanemployeeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_AchievedSpecifiedImprovementInTotalShareholderReturnTimeFrameAxis=pnm_Achievesaspecificperformancetargetbytheendof2017andsheremainsanemployeeMemberMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_TitleOfIndividualAxis=pnm_ExecutiveVicePresidentandChiefFinancialOfficerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_AchievedspecifiedperformancetargettimeframeAxis=pnm_Achievedperformancetargetfor2015and2016Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnm_AchievedspecifiedperformancetargettimeframeAxis=pnm_Achievedperformancetargetfor20152016and2017Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_RetainedEarningsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201609Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

X
- Details
Name: | us-gaap_AwardTypeAxis=pnm_RestrictedStockAndPerformanceSharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_TitleOfIndividualAxis=us-gaap_ManagementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=pnm_MarketBasedSharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PlanNameAxis=pnm_PerformanceEquityPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |