Debt Instrument, Number of Lending Banks

No definition available.

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- Definition

Invested Cash and Cash Equivalents

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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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

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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

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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

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the assets received as collateral against securities loaned to other broker-dealers. Borrowers of securities generally are required to provide collateral to the lenders of securities, commonly cash but sometimes other securities or standby letters of credit, with a value slightly higher than that of the securities borrowed. In instances where the entity is permitted to sell or re-pledge these securities, the entity reports the fair value of the collateral received and the related obligation to return the collateral as a liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 10
-Section 05
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=64836671&loc=d3e93645-111703

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

+ Details

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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

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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

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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

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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- Details

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Balance Type:
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- Details

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Balance Type:
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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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- Details

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- Details

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Financing - Borrowing Arrangements Between PNMR and Its Subsidiaries and Short-term Debt (Details)	Nov. 01, 2020 USD ($)	Feb. 21, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 21, 2016 USD ($)	Nov. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jan. 08, 2014 USD ($) bank
Short-term Debt [Line Items]
Short-term debt			$ 287,100,000			$ 250,600,000
Letters of credit outstanding			6,200,000
JPMorgan Chase Bank, N.A. [Member]
Short-term Debt [Line Items]
Letters of credit outstanding			30,300,000
PNMR Term Loan Agreement [Member]
Short-term Debt [Line Items]
Short-term debt			0			150,000,000
PNMR 2016 One Year Term Loan [Member]
Short-term Debt [Line Items]
Short-term debt			100,000,000	$ 100,000,000.0
PNMR Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Financing capacity			300,000,000		$ 10,000,000.0
Short-term debt			126,100,000			41,600,000
PNMR Revolving Credit Facility [Member] \| Scenario, Forecast [Member]
Short-term Debt [Line Items]
Financing capacity	$ 290,000,000.0
Subsequent Event [Member]
Short-term Debt [Line Items]
Invested cash		$ 1,500,000
Subsequent Event [Member] \| PNMR Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Available borrowing capacity		149,500,000
Subsequent Event [Member] \| Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Available borrowing capacity		607,600,000
Texas-New Mexico Power Company [Member]
Short-term Debt [Line Items]
Subsidiary loan agreements			4,600,000			11,800,000
Short-term debt			0			59,000,000
Letters of credit outstanding			100,000
Texas-New Mexico Power Company [Member] \| TNMP Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Financing capacity			75,000,000
Short-term debt			0			59,000,000
Texas-New Mexico Power Company [Member] \| TNMP Revolving Credit Facility [Member] \| First Mortgage Bonds Due 2019, Series 2009A, at 9.50% [Member]
Short-term Debt [Line Items]
Aggregate principal amount of bonds			75,000,000
Texas-New Mexico Power Company [Member] \| Subsequent Event [Member]
Short-term Debt [Line Items]
Subsidiary loan agreements		7,400,000
Invested cash		0
Texas-New Mexico Power Company [Member] \| Subsequent Event [Member] \| TNMP Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Available borrowing capacity		66,900,000
Public Service Company of New Mexico [Member]
Short-term Debt [Line Items]
Subsidiary loan agreements			0
Short-term debt			61,000,000			0
Letters of credit outstanding			$ 2,500,000
Public Service Company of New Mexico [Member] \| New Mexico Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Financing capacity							$ 50,000,000.0
Number of participating lenders (in banks) \| bank							9
Public Service Company of New Mexico [Member] \| Local Lines of Credit [Member]
Short-term Debt [Line Items]
Interest rates on outstanding borrowings			1.81%
Public Service Company of New Mexico [Member] \| PNM Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Financing capacity			$ 400,000,000		$ 40,000,000.0
Interest rates on outstanding borrowings			1.82%
Short-term debt			$ 35,000,000			0
Public Service Company of New Mexico [Member] \| PNM Revolving Credit Facility [Member] \| Scenario, Forecast [Member]
Short-term Debt [Line Items]
Financing capacity	$ 360,000,000.0
Public Service Company of New Mexico [Member] \| New Mexico Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Short-term debt			26,000,000			0
Public Service Company of New Mexico [Member] \| Subsequent Event [Member]
Short-term Debt [Line Items]
Subsidiary loan agreements		0
Invested cash		0
Public Service Company of New Mexico [Member] \| Subsequent Event [Member] \| PNM Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Available borrowing capacity		366,200,000
Public Service Company of New Mexico [Member] \| Subsequent Event [Member] \| New Mexico Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Available borrowing capacity		$ 25,000,000
PNM Resources [Member]
Short-term Debt [Line Items]
Short-term debt			$ 226,100,000			$ 191,600,000
PNM Resources [Member] \| PNMR Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Interest rates on outstanding borrowings			1.98%
Maximum [Member]
Short-term Debt [Line Items]
Subsidiary loan agreements			$ 100,000,000