Regulatory and Rate Matters - San Juan Generating Station Unit 1 Outage (Details) - San Juan Generating Station $ in Millions	Mar. 31, 2022 USD ($)
San Juan Generating Station Owners \| Insurance Deductible
Public Utilities, Commitments And Contingencies [Line Items]
Estimate of possible loss	$ 2.0
PNM \| Insurance Deductible
Public Utilities, Commitments And Contingencies [Line Items]
Estimate of possible loss	$ 1.0
PNM \| San Juan Generating Station Unit 1
Public Utilities, Commitments And Contingencies [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	50.00%

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12021-110248

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