Debt Instrument, Covenant, Debt To Capitalization Ratio

No definition available.

Name:	pnm_DebtInstrumentCovenantDebtToCapitalizationRatio
Namespace Prefix:	pnm_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Series Of Bond Issuance

+ References

No definition available.

+ Details

Name:	pnm_DebtInstrumentSeriesOfBondIssuance
Namespace Prefix:	pnm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Public Utilities, Maturity Term Over Which Financings Require Regulator Approval

+ References

No definition available.

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124429444&loc=SL124452920-239629

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69C
-URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495737-112612

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69B
-URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123466204&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124429444&loc=SL124452920-239629

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of hedged item in hedging relationship. Excludes hedged asset or liability.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeAmountOfHedgedItem
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Nominal or face amount used to calculate payments on the derivative asset.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeAssetNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of derivative instruments of a particular derivative asset or group of derivative assets held by the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959

+ Details

Name:	us-gaap_DerivativeAssetNumberOfInstrumentsHeld
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeFixedInterestRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Aggregate fair value of all derivative assets designated as hedging instruments. Includes instruments designated as cash flow hedges, fair value hedges, and hedges of net investments in foreign operations.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeInstrumentsInHedgesAssetsAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI https://asc.fasb.org/extlink&oid=123466204&loc=SL6031897-161870

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69C
-URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495737-112612

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69B
-URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1D
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3255-108585

+ Details

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

- Definition

The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3255-108585

+ Details

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

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3291-108585

+ Details

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

Financing - Financing Activities (Details)										9 Months Ended	12 Months Ended
Financing - Financing Activities (Details)	Oct. 31, 2022 USD ($) derivative	Sep. 30, 2022 USD ($) derivative	Aug. 05, 2022 USD ($)	May 20, 2022 USD ($)	May 02, 2022 USD ($) derivative	Jan. 24, 2022 USD ($)	Jun. 18, 2021 USD ($)	Mar. 09, 2021 USD ($)	Dec. 22, 2020 USD ($)	Sep. 30, 2022 USD ($) derivative	Dec. 31, 2021 USD ($)	Oct. 21, 2022 USD ($)	Jun. 01, 2022 USD ($) derivative	Apr. 27, 2022 USD ($) bond	Aug. 16, 2021 USD ($)	Jul. 14, 2021 USD ($)	May 18, 2021 USD ($)	Mar. 09, 2018 USD ($)
Debt Instrument [Line Items]
Financing capacity																	$ 40,000,000
Subsequent event
Debt Instrument [Line Items]
Remaining borrowing capacity												$ 777,700,000
Interest rate contract \| Cash Flow Hedge
Debt Instrument [Line Items]
Number of instruments held \| derivative													2
Variable Rate Debt \| Interest rate contract \| Cash Flow Hedge
Debt Instrument [Line Items]
Number of instruments held \| derivative		2			2					2
Term of loan		15 months		19 months	20 months
Derivative asset, notional amount		$ 200,000,000								$ 200,000,000
Derivative, notional amount				$ 100,000,000
Fixed interest rate				2.52%	2.65%
Derivative instruments in hedges, fair value		$ 8,600,000								$ 8,600,000
Variable Rate Debt, Tranche 1 \| Interest rate contract \| Cash Flow Hedge
Debt Instrument [Line Items]
Variable interest rate		4.17%								4.17%
Derivative asset, notional amount		$ 100,000,000			$ 150,000,000					$ 100,000,000
Variable Rate Debt, Tranche 2 \| Interest rate contract \| Cash Flow Hedge
Debt Instrument [Line Items]
Variable interest rate		4.18%								4.18%
Derivative asset, notional amount		$ 100,000,000			$ 200,000,000					$ 100,000,000
PNMR 2020 Delayed-Draw Term Loan
Debt Instrument [Line Items]
Aggregate principal amount									$ 300,000,000
Proceeds from issuance of debt									$ 80,000,000
Remaining borrowing capacity								$ 220,000,000
Fixed Rate Debt \| Interest rate contract \| Cash Flow Hedge \| Subsequent event
Debt Instrument [Line Items]
Number of instruments held \| derivative	2
Term of loan	14 months
Fixed Rate Debt, Tranche 1 \| Interest rate contract \| Cash Flow Hedge \| Subsequent event
Debt Instrument [Line Items]
Derivative asset, notional amount	$ 100,000,000
Fixed interest rate	4.66%
Fixed Rate, Tranche 2 \| Interest rate contract \| Cash Flow Hedge \| Subsequent event
Debt Instrument [Line Items]
Derivative asset, notional amount	$ 200,000,000
Fixed interest rate	4.65%
PNM
Debt Instrument [Line Items]
Maturity term over which financings require regulator approval (more than)										18 months
PNM \| Subsequent event
Debt Instrument [Line Items]
Remaining borrowing capacity												400,000,000
Texas-New Mexico Power Company \| Subsequent event
Debt Instrument [Line Items]
Remaining borrowing capacity												$ 96,500,000
Line of credit
Debt Instrument [Line Items]
Ratio of debt to capital (less than or equal to)										70.00%
Line of credit \| PNM 2022 Delayed-Draw Term Loan \| Revolving credit facility
Debt Instrument [Line Items]
Financing capacity			$ 225,000,000
Proceeds from long-term lines of credit		45,000,000	$ 180,000,000
Line of credit \| Variable Rate Debt
Debt Instrument [Line Items]
Hedging arrangement		$ 650,000,000								$ 650,000,000
Line of credit \| PNMR 2021 Delayed-Draw Term Loan \| Revolving credit facility
Debt Instrument [Line Items]
Financing capacity																	$ 1,000,000,000
Proceeds from long-term lines of credit						$ 100,000,000					$ 900,000,000
Line of credit \| PNM and TNMP
Debt Instrument [Line Items]
Ratio of debt to capital (less than or equal to)										65.00%
Bonds \| PNMR 2021 Delayed-Draw Term Loan
Debt Instrument [Line Items]
Variable interest rate		4.13%								4.13%
Bonds \| PNM \| Pollution Control Revenue Bonds
Debt Instrument [Line Items]
Long-term debt											104,500,000		$ 31,500,000
Bonds \| PNM \| Pollution Control Revenue Bonds Due June Twenty Thirty Eight
Debt Instrument [Line Items]
Aggregate principal amount											$ 36,000,000		36,000,000
Stated interest rate											1.05%
Bonds \| PNM \| Pollution Control Revenue Bonds Due June Twenty Forty
Debt Instrument [Line Items]
Aggregate principal amount											$ 37,000,000		$ 37,000,000
Stated interest rate											2.125%
Bonds \| PNM \| Pollution Control Revenue Bonds Due June Twenty Forty, City Of Farmington, NM
Debt Instrument [Line Items]
Aggregate principal amount											$ 11,500,000
Stated interest rate											1.20%
Bonds \| PNM \| Pollution Control Revenue Bonds Due June Twenty Forty Two
Debt Instrument [Line Items]
Aggregate principal amount											$ 20,000,000
Stated interest rate											2.45%
Bonds \| PNM \| Pollution Control Revenue Bonds Due June Twenty Twenty Four
Debt Instrument [Line Items]
Stated interest rate													3.00%
Bonds \| PNM \| PNM 2021 75 Million Term Loan
Debt Instrument [Line Items]
Variable interest rate		3.53%								3.53%
Bonds \| Texas-New Mexico Power Company \| TNMP 2022 Bond Purchase Agreement
Debt Instrument [Line Items]
Aggregate principal amount														$ 160,000,000
Debt instrument, series of bond issuance \| bond														2
Bonds \| Texas-New Mexico Power Company \| TNMP 2022 Bond Purchase Agreement at 4.13% Due May 12, 2022
Debt Instrument [Line Items]
Aggregate principal amount														$ 65,000,000
Stated interest rate														4.13%
Bonds \| Texas-New Mexico Power Company \| TNMP 2022 Bond Purchase Agreement at 3.81% Due July 28, 2032
Debt Instrument [Line Items]
Aggregate principal amount														$ 95,000,000
Stated interest rate														3.81%
Mortgage Bonds \| Texas-New Mexico Power Company \| TNMP 2021 Bond Purchase Agreement
Debt Instrument [Line Items]
Aggregate principal amount															$ 65,000,000	$ 65,000,000
Stated interest rate															2.44%
Senior Notes \| PNM \| PNM 2021 Note Purchase Agreement
Debt Instrument [Line Items]
Aggregate principal amount																160,000,000
Senior Notes \| PNM \| PNM 2021 SUNs At 2.59 Percent Due July 15, 2033
Debt Instrument [Line Items]
Aggregate principal amount																$ 80,000,000
Stated interest rate																2.59%
Senior Notes \| PNM \| PNM 2021 SUNs At 3.14 Percent Due July 15, 2041
Debt Instrument [Line Items]
Aggregate principal amount																$ 80,000,000
Stated interest rate																3.14%
Senior Notes \| PNM \| PNM 2021 SUNs At 5.35 Percent Due October 1, 2021
Debt Instrument [Line Items]
Aggregate principal amount																$ 160,000,000
Stated interest rate																5.35%
Senior Notes \| PNM \| PNM 2019 40 Million Term Loan
Debt Instrument [Line Items]
Repayments of debt							$ 40,000,000
Term loan agreement with banks \| PNM \| PNM 2021 75 Million Term Loan
Debt Instrument [Line Items]
Aggregate principal amount							$ 75,000,000
Unsecured Debt \| PNMR 2018 SUNS 3.25% due March 2021
Debt Instrument [Line Items]
Aggregate principal amount																		$ 300,000,000
Stated interest rate																		3.25%
Repayments of debt								$ 80,000,000