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, Prepayment Period

+ References

No definition available.

+ Details

Name:	pnm_DebtInstrumentPrepaymentPeriod
Namespace Prefix:	pnm_
Data Type:	xbrli:durationItemType
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 http://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 http://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 http://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 http://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 http://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 http://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 http://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 http://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 http://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 http://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

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=123599511&loc=d3e64711-112823

+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of principal amount of debt redeemed.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The effective interest rate at the end of the reporting period.

+ 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 http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
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

+ 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, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ 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 http://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 http://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 http://asc.fasb.org/extlink&oid=120400017&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 http://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 http://asc.fasb.org/extlink&oid=120398452&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 http://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 http://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 http://asc.fasb.org/extlink&oid=123570139&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 http://asc.fasb.org/extlink&oid=123570139&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 http://asc.fasb.org/extlink&oid=123570139&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)											6 Months Ended
Financing - Financing Activities (Details)	Jul. 14, 2021 USD ($) bond_series	Jun. 30, 2021 USD ($)	Jun. 18, 2021 USD ($)	May 18, 2021 USD ($)	Mar. 09, 2021 USD ($)	Dec. 22, 2020 USD ($)	Jun. 22, 2020 USD ($)	Apr. 30, 2020 USD ($)	Apr. 15, 2020 USD ($)	Jan. 01, 2020	Jun. 30, 2021 USD ($)	Aug. 16, 2021 USD ($) bond_series	Jul. 23, 2021 USD ($)	Dec. 21, 2020 USD ($)	Aug. 31, 2020 USD ($)	Jul. 15, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jun. 01, 2020 USD ($)	Apr. 24, 2020 USD ($) bond_series	Dec. 31, 2019 USD ($) bond_series	Mar. 09, 2018 USD ($)
Debt Instrument [Line Items]
Financing capacity		$ 40,000,000.0									$ 40,000,000.0
Subsequent event
Debt Instrument [Line Items]
Remaining borrowing capacity													$ 715,200,000
PNMR 2020 Delayed-Draw Term Loan
Debt Instrument [Line Items]
Aggregate principal amount						$ 300,000,000.0
Proceeds from issuance of debt						$ 80,000,000.0
Remaining borrowing capacity					$ 220,000,000.0
PNM \| Subsequent event
Debt Instrument [Line Items]
Remaining borrowing capacity													397,800,000
PNM \| PNM 2019 40 Million Term Loan
Debt Instrument [Line Items]
Repayments of debt			$ 40,000,000.0
PNM \| Maximum
Debt Instrument [Line Items]
Maturity term over which financings require regulator approval (more than)											18 months
Texas-New Mexico Power Company \| Subsequent event
Debt Instrument [Line Items]
Remaining borrowing capacity													18,500,000
Line of credit
Debt Instrument [Line Items]
Ratio of debt to capital (less than or equal to)											70.00%
Line of credit \| PNMR 2021 Delayed-Draw Term Loan \| Revolving credit facility
Debt Instrument [Line Items]
Financing capacity				$ 1,000,000,000.0
Line of credit \| PNMR 2020 Delayed-Draw Term Loan \| Revolving credit facility
Debt Instrument [Line Items]
Proceeds from long-term lines of credit		$ 850,000,000.0
Line of credit facility, interest rate at period end		0.93%									0.93%
Line of credit \| PNMR Revolving Credit Facility \| Revolving credit facility
Debt Instrument [Line Items]
Repayments of debt				92,100,000
Line of credit \| PNMR Development Revolving Credit Facility \| Revolving credit facility
Debt Instrument [Line Items]
Repayments of debt				40,000,000.0
Line of credit \| PNM and TNMP
Debt Instrument [Line Items]
Ratio of debt to capital (less than or equal to)											65.00%
Line of credit \| PNM \| PNM Revolving Credit Facility
Debt Instrument [Line Items]
Repayments of debt								$ 100,000,000.0
Mortgage Bonds \| Texas-New Mexico Power Company \| TNMP 2021 Bond Purchase Agreement \| Forecast
Debt Instrument [Line Items]
Aggregate principal amount												$ 65,000,000.0
Debt instrument, series of bond issuance \| bond_series												1
Stated interest rate												2.44%
Mortgage Bonds \| Texas-New Mexico Power Company \| TNMP 2020 Bond Purchase Agreement
Debt Instrument [Line Items]
Aggregate principal amount																			$ 185,000,000.0
Debt instrument, series of bond issuance \| bond_series																			4
Mortgage Bonds \| Texas-New Mexico Power Company \| TNMP 2020 Bond Purchase Agreement, Bond Series 1 and 2
Debt Instrument [Line Items]
Aggregate principal amount																			$ 110,000,000.0
Mortgage Bonds \| Texas-New Mexico Power Company \| TNMP 2020 Bond Purchase Agreement, Bond Series 3 and 4
Debt Instrument [Line Items]
Aggregate principal amount																$ 75,000,000.0
Mortgage Bonds \| Texas-New Mexico Power Company \| TNMP First Mortgage Bonds
Debt Instrument [Line Items]
Aggregate principal amount		$ 750,000,000.0									$ 750,000,000.0
Debt instrument, prepayment period											30 days
Debt instrument, redemption price, percentage of principal amount redeemed											100.00%
Senior Notes \| PNM 2021 SUNs at 2.59% due July 15, 2033 \| Subsequent event
Debt Instrument [Line Items]
Aggregate principal amount	$ 80,000,000.0
Stated interest rate	2.59%
Senior Notes \| PNM 2021 SUNs at 3.14% due July 15, 2041 \| Subsequent event
Debt Instrument [Line Items]
Aggregate principal amount	$ 80,000,000.0
Stated interest rate	3.14%
Senior Notes \| PNM SUNs at 5.35% due October 1, 2021 \| Subsequent event
Debt Instrument [Line Items]
Stated interest rate	5.35%
Repayments of debt	$ 160,000,000.0
Senior Notes \| Senior Unsecured Notes, 3.21% Series A, due April 2030
Debt Instrument [Line Items]
Aggregate principal amount								$ 150,000,000.0
Stated interest rate								3.21%
Senior Notes \| Senior Unsecured Notes, 3.57% Series B, due April 2039
Debt Instrument [Line Items]
Aggregate principal amount								$ 50,000,000.0
Stated interest rate								3.57%
Senior Notes \| PNM
Debt Instrument [Line Items]
Aggregate principal amount								$ 200,000,000.0
Senior Notes \| PNM \| PNM 2021 Note Purchase Agreement \| Subsequent event
Debt Instrument [Line Items]
Aggregate principal amount	$ 160,000,000.0
Debt instrument, series of bond issuance \| bond_series	2
Senior Notes \| PNM \| PNM 2020 250 Million Term Loan
Debt Instrument [Line Items]
Repayments of debt								100,000,000.0
Proceeds from issuance of debt								$ 100,000,000.0
Term loan agreement with banks \| PNM \| PNM 2021 75 Million Term Loan
Debt Instrument [Line Items]
Aggregate principal amount			$ 75,000,000.0
Variable interest rate		0.91%									0.91%
Bonds
Debt Instrument [Line Items]
Repayments of debt							$ 302,500,000
Bonds \| City of Farmington, New Mexico
Debt Instrument [Line Items]
Aggregate principal amount																		$ 266,500,000
Bonds \| PNMR 2021 Delayed-Draw Term Loan
Debt Instrument [Line Items]
Variable interest rate		0.93%									0.93%
Bonds \| PNMR 2020 Delayed-Draw Term Loan
Debt Instrument [Line Items]
Repayments of debt				300,000,000.0
Bonds \| PNMR 2019 Term Loan
Debt Instrument [Line Items]
Repayments of debt				150,000,000.0
Bonds \| PNMR 2020 Term Loan
Debt Instrument [Line Items]
Repayments of debt				150,000,000.0
Bonds \| Pollution Control Revenue Bonds
Debt Instrument [Line Items]
Stated interest rate		0.08%									0.08%
Variable interest rate		0.08%									0.08%
Term loans																				$ 100,300,000
Bonds \| Pollution Control Revenue Bonds \| Subsequent event
Debt Instrument [Line Items]
Aggregate principal amount													$ 100,300,000
Bonds \| Pollution Control Revenue Bonds, Due 2040
Debt Instrument [Line Items]
Debt instrument, series of bond issuance \| bond_series																				2
Term loans																				$ 40,000,000.0
Bonds \| Pollution Control Revenue Bonds, Due 2043, Series 1
Debt Instrument [Line Items]
Term loans																				39,300,000
Bonds \| Pollution Control Revenue Bonds, Due 2043, Series 2
Debt Instrument [Line Items]
Term loans																				21,000,000.0
Bonds \| Pollution Control Revenue Bonds at 6.25% \| Maricopa County, Arizona Pollution Control Corporation
Debt Instrument [Line Items]
Aggregate principal amount																	$ 36,000,000.0			$ 36,000,000.0
Stated interest rate																	6.25%			6.25%
Debt instrument, redemption price, percentage										101.00%
Bonds \| Pollution Control Revenue Bonds at 6.25% \| City of Farmington, New Mexico
Debt Instrument [Line Items]
Aggregate principal amount																	$ 11,500,000			$ 11,500,000
Stated interest rate																	6.25%			6.25%
Bonds \| Pollution Control Revenue Bonds at 5.90% \| City of Farmington, New Mexico
Debt Instrument [Line Items]
Aggregate principal amount																	$ 255,000,000.0			$ 255,000,000.0
Stated interest rate																	5.90%			5.90%
Bonds \| PNM \| PNM 2021 75 Million Term Loan
Debt Instrument [Line Items]
Variable interest rate		0.91%									0.91%
Medium-term Notes \| PNMR Development Term Loan
Debt Instrument [Line Items]
Repayments of debt				$ 65,000,000.0
Medium-term Notes \| PNM \| PNM 2020 250 Million Term Loan
Debt Instrument [Line Items]
Aggregate principal amount									$ 250,000,000.0					$ 150,000,000.0
Medium-term Notes \| PNM \| PNM 2019 Term Loan
Debt Instrument [Line Items]
Repayments of debt									$ 250,000,000.0
Letter of credit \| WFB LOC Facility
Debt Instrument [Line Items]
Aggregate principal amount															$ 30,300,000
Unsecured Debt \| PNMR 2018 SUNS 3.25% due March 2021
Debt Instrument [Line Items]
Aggregate principal amount																					$ 300,000,000.0
Stated interest rate																					3.25%
Repayments of debt					$ 80,000,000.0