Debt Instruments, NMPRC Approved credit facility

No definition available.

Name:	pnm_DebtInstrumentsNMPRCApprovedcreditfacility
Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Short Term Debt Due to Related Party

+ References

No definition available.

+ Details

Name:	pnm_ShortTermDebtDueToRelatedParty
Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of assets pledged to secure a debt instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

+ Details

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

- 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

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

The cash inflow from a borrowing having initial term of repayment within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

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

- Definition

Cash and investments whose use in whole or in part is restricted for the long-term, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

+ References

No definition available.

+ Details

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

- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ 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(19)(a))
-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 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_ShortTermBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_ShortTermDebtLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of short-term debt outstanding.

+ References

+ Details

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

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=pnm_PnmrTermLoanAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_NotesPayableToBanksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=us-gaap_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=pnm_PNMRRevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_RevolvingCreditFacilityMember
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:	us-gaap_DebtInstrumentAxis=pnm_LocalLinesOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=pnm_PNMRevolvingCreditFacilityMember
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:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_AffiliatedEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=pnm_FirstMortgageBondsDue2014Series2009AAt9Point50PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Financing - Short-term Debt (Details) - USD ($)	9 Months Ended
Financing - Short-term Debt (Details) - USD ($)	Sep. 30, 2016	Oct. 21, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Short-term debt	$ 355,900,000		$ 250,600,000
Letters of credit outstanding	$ 36,500,000
Subsequent event [Member]
Short-term Debt [Line Items]
Remaining borrowing capacity		$ 592,800,000
PNMR Term Loan Agreement [Member]
Short-term Debt [Line Items]
Weighted-average interest rate for short-term debt	1.38%
Short-term debt	$ 150,000,000		150,000,000
Notes Payable to Banks [Member] \| PNMR Term Loan Agreement [Member]
Short-term Debt [Line Items]
Term of loan	12 months
Borrowings under 12-month term loan	$ 150,000,000.0
PNM Resources [Member] \| Subsequent event [Member]
Short-term Debt [Line Items]
Remaining borrowing capacity		100,400,000
Consolidated invested cash		1,800,000
PNM Resources [Member] \| PNMR Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Weighted-average interest rate for short-term debt	1.78%
PNM Resources [Member] \| Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Financing capacity	$ 300,000,000.0
Short-term debt	163,500,000		41,600,000
Public Service Company of New Mexico [Member]
Short-term Debt [Line Items]
Short-term debt	42,400,000		0
Letters of credit outstanding	2,500,000
Public Service Company of New Mexico [Member] \| Subsequent event [Member]
Short-term Debt [Line Items]
Remaining borrowing capacity		373,500,000
Consolidated invested cash		0
Public Service Company of New Mexico [Member] \| Local Lines of Credit [Member]
Short-term Debt [Line Items]
NMPRC approved credit facility	$ 50,000,000
Weighted-average interest rate for short-term debt	1.68%
Short-term debt	$ 20,000,000		0
Public Service Company of New Mexico [Member] \| Local Lines of Credit [Member] \| Subsequent event [Member]
Short-term Debt [Line Items]
Remaining borrowing capacity		44,000,000
Public Service Company of New Mexico [Member] \| PNMR Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Weighted-average interest rate for short-term debt	1.66%
Public Service Company of New Mexico [Member] \| Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Financing capacity	$ 400,000,000.0
Short-term debt	22,400,000		0
Texas-New Mexico Power Company [Member]
Short-term Debt [Line Items]
Short-term debt	0		59,000,000
Letters of credit outstanding	100,000
Short-term debt – affiliate	0		11,800,000
Texas-New Mexico Power Company [Member] \| Subsequent event [Member]
Short-term Debt [Line Items]
Remaining borrowing capacity		74,900,000
Consolidated invested cash		300,000
Texas-New Mexico Power Company [Member] \| Subsequent event [Member] \| Affiliated Entity [Member]
Short-term Debt [Line Items]
Short-term debt – affiliate		$ 0
Texas-New Mexico Power Company [Member] \| Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Financing capacity	75,000,000.0
Short-term debt	0		$ 59,000,000
Texas-New Mexico Power Company [Member] \| Revolving Credit Facility [Member] \| First Mortgage Bonds, Due 2014, Series 2009A, at 9.50% [Member]
Short-term Debt [Line Items]
Collateral amount	$ 75,000,000