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 amount for notes payable (written promise to pay), due to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

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 210.5-02.19(a)(5))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_NotesPayableRelatedPartiesClassifiedCurrent
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:
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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_IntercompanyLoanAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=pnm_FirstMortgageBondsDue2014Series2009AAt9Point50PercentMember
Namespace Prefix:
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Financing - Short-term Debt (Details) - USD ($)	6 Months Ended
Financing - Short-term Debt (Details) - USD ($)	Jun. 30, 2016	Aug. 05, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Short-term debt	$ 401,400,000		$ 250,600,000
Letters of credit outstanding	$ 46,200,000
Subsequent Event [Member]
Short-term Debt [Line Items]
Remaining borrowing capacity		$ 534,800,000
PNMR Term Loan Agreement [Member]
Short-term Debt [Line Items]
Weighted-average interest rate for short-term debt	1.31%
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		115,300,000
Consolidated invested cash		1,500,000
PNM Resources [Member] \| PNMR Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Weighted-average interest rate for short-term debt	1.70%
PNM Resources [Member] \| Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Financing capacity	$ 300,000,000.0
Short-term debt	95,400,000		41,600,000
Public Service Company of New Mexico [Member]
Short-term Debt [Line Items]
Short-term debt	126,000,000		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		329,600,000
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	1.58%
Short-term debt	$ 15,000,000		0
Public Service Company of New Mexico [Member] \| Local Lines of Credit [Member] \| Subsequent Event [Member]
Short-term Debt [Line Items]
Remaining borrowing capacity		15,000,000
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	1.58%
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	111,000,000		0
Texas-New Mexico Power Company [Member]
Short-term Debt [Line Items]
Short-term debt	30,000,000		59,000,000
Letters of credit outstanding	100,000
Short-term debt – affiliate	11,500,000		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		0
Texas-New Mexico Power Company [Member] \| Subsequent Event [Member] \| Affiliated Entity [Member]
Short-term Debt [Line Items]
Short-term debt – affiliate		$ 1,400,000
Texas-New Mexico Power Company [Member] \| Intercompany loan agreements [Member]
Short-term Debt [Line Items]
Short-term debt - affiliate	$ 11,500,000.0
Texas-New Mexico Power Company [Member] \| TNMP Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Weighted-average interest rate for short-term debt	1.46%
Texas-New Mexico Power Company [Member] \| Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Financing capacity	$ 75,000,000.0
Short-term debt	30,000,000		$ 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