Final Reclamation, capped amount to be collected

No definition available.

Name:	pnm_FinalReclamationCappedAmountToBeCollected
Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Public Utilities, Annual Funding

+ References

No definition available.

+ Details

Name:	pnm_PublicUtilitiesAnnualFunding
Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	pnm_PublicUtilitiesCommitmentsAndContingenciesLineItems
Namespace Prefix:	pnm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Public Utilities, Estimated Increase in Coal Cost, Percentage

+ References

No definition available.

+ Details

Name:	pnm_PublicUtilitiesEstimatedIncreaseinCoalCostPercentage
Namespace Prefix:	pnm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Public Utilities, Expected Funding Annual Requirements

+ References

No definition available.

+ Details

Name:	pnm_PublicUtilitiesExpectedFundingAnnualRequirements
Namespace Prefix:	pnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

+ Details

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

- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

+ Details

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

- Definition

Aggregate carrying amount, as of the balance sheet date, of current assets not separately disclosed in the balance sheet. Current assets are expected to be realized or consumed 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 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.8)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 8

-Article 5

+ Details

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

- Definition

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

+ Details

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

- Details

Name:	dei_LegalEntityAxis=pnm_PublicServiceCompanyOfNewMexicoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_JointlyOwnedUtilityPlantAxis=pnm_SanJuanGeneratingStationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments and Contingencies - Coal Supply (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Public Utilities, Commitments And Contingencies [Line Items]
Other current assets	$ 65,264,000us-gaap_OtherAssetsCurrent	$ 58,471,000us-gaap_OtherAssetsCurrent
Public Service Company of New Mexico [Member] \| Surface [Member]
Public Utilities, Commitments And Contingencies [Line Items]
Regulatory Assets	100,000,000
Public Service Company of New Mexico [Member] \| Loss on Long-term Purchase Commitment [Member] \| Surface [Member]
Public Utilities, Commitments And Contingencies [Line Items]
Loss Contingency Accrual	25,600,000	25,700,000
Final Reclamation, capped amount to be collected	100,000,000
Public Service Company of New Mexico [Member] \| Loss on Long-term Purchase Commitment [Member] \| Underground [Member]
Public Utilities, Commitments And Contingencies [Line Items]
Loss Contingency Accrual	8,800,000	8,600,000
Public Service Company of New Mexico [Member] \| Loss on Long-term Purchase Commitment [Member]
Public Utilities, Commitments And Contingencies [Line Items]
Public Utilities, Annual Funding		1,000,000	300,000	3,500,000
Public Utilities, Expected Funding Annual Requirements	600,000
San Juan Generating Station [Member] \| Public Service Company of New Mexico [Member] \| Loss on Long-term Purchase Commitment [Member] \| Surface [Member]
Public Utilities, Commitments And Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss	57,000,000
San Juan Generating Station [Member] \| Public Service Company of New Mexico [Member] \| Loss on Long-term Purchase Commitment [Member] \| Underground [Member]
Public Utilities, Commitments And Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss	93,300,000
San Juan Generating Station [Member] \| Coal Supply [Member] \| Public Service Company of New Mexico [Member]
Public Utilities, Commitments And Contingencies [Line Items]
Other current assets	$ 38,900,000	$ 37,300,000
Public Utilities, Estimated Increase in Coal Cost, Percentage	30.00%