Debt Instrument, Interest Rate at Period End 1

No definition available.

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Period Type:	instant

- Definition

Payments to fund long-term loans to unaffiliated third party

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Public Utilities, Maturity term over which financings require regulator approval

+ References

No definition available.

+ Details

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- Definition

Ratio of debt to capital, maximum

+ References

No definition available.

+ Details

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Namespace Prefix:	pnm_
Data Type:	num:percentItemType
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/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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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/presentationRef
-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=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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

- Definition

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

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num: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

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

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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/presentationRef
-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=6879938&loc=d3e572229-122910

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(16))
-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 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

+ Details

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

- Definition

Maximum period the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, 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 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Amount of unrealized gain (loss) related to the increase or decrease in fair value of interest rate derivatives designated as cash flow hedging instruments, which was recorded in accumulated other comprehensive income to the extent that the cash flow hedge was determined to be effective.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

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- Details

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- Details

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- Details

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- Details

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- Details

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Financing - Financing Activities (Details) - USD ($)			1 Months Ended	3 Months Ended	12 Months Ended
Financing - Financing Activities (Details) - USD ($)	Mar. 09, 2017	Feb. 01, 2016	Mar. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Oct. 21, 2016	Sep. 30, 2015	Mar. 09, 2015
Debt Instrument [Line Items]
Fixed interest rate							1.927%
Estimated principal payments			$ 283,500,000	$ 283,500,000
PNMR 2015 Term Loan Agreement
Debt Instrument [Line Items]
Interest rate at period end			1.75%	1.75%
PNMR 2016 Two-Year Term Loan
Debt Instrument [Line Items]
Term loans			$ 100,000,000.0	$ 100,000,000.0
Interest rate			1.93%	1.93%
Variable rate short-term debt
Debt Instrument [Line Items]
Fixed interest rate	1.926%
Aggregate principal amount	$ 50,000,000.0
Term of hedging agreement	4 years
Cash flow hedge \| Level 2
Debt Instrument [Line Items]
Fair value gain (loss)			$ (400,000)	$ 200,000	$ (100,000)
PNM
Debt Instrument [Line Items]
Estimated principal payments			232,000,000	$ 232,000,000
PNM \| Maximum
Debt Instrument [Line Items]
Maturity term over which financings require regulator approval (more than)				18 months
NM Capital \| Coal supply \| San Juan Coal Company, Westmoreland
Debt Instrument [Line Items]
Payments to fund long-term loans to unaffiliated third party		$ 125,000,000.0
Line of credit
Debt Instrument [Line Items]
Ratio of debt to capital (less than or equal to)				65.00%
PNMR 2015 Term Loan Agreement
Debt Instrument [Line Items]
Term loans								$ 150,000,000.0
PNM 2016 Term Loan Agreement [Member] \| PNM
Debt Instrument [Line Items]
Aggregate principal amount			$ 175,000,000.0	$ 175,000,000.0
Interest rate			1.59%	1.59%
BTMU Term Loan Agreement \| NM Capital
Debt Instrument [Line Items]
Term loans		$ 125,000,000.0	$ 82,800,000	$ 82,800,000
Stated interest rate			3.79%	3.79%
Estimated principal payments			$ 33,500,000	$ 33,500,000
Letter of credit \| PNMR \| JPM LOC Facility
Debt Instrument [Line Items]
Aggregate principal amount						$ 30,300,000.0