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Commitments and Contingencies - Coal Supply (Details) - USD ($)
 6 Months Ended 12 Months Ended
Jun. 30, 2023
Dec. 31, 2022
Jan. 31, 2016
PNM | Loss on long-term purchase commitment | Surface      
Public Utilities, Commitments And Contingencies [Line Items]      
Loss contingency accrual $ 56,600,000 $ 62,600,000  
PNM | Loss on long-term purchase commitment | Underground      
Public Utilities, Commitments And Contingencies [Line Items]      
Loss contingency accrual 28,600,000 28,200,000  
PNM | Loss on long-term purchase commitment | San Juan Generating Station | Surface      
Public Utilities, Commitments And Contingencies [Line Items]      
Estimate of possible loss 60,900,000    
PNM | Loss on long-term purchase commitment | San Juan Generating Station | Underground      
Public Utilities, Commitments And Contingencies [Line Items]      
Estimate of possible loss 33,300,000    
Coal supply | San Juan Generating Station      
Public Utilities, Commitments And Contingencies [Line Items]      
Cash used to support bank letter or credit arrangement     $ 30,300,000
Coal supply | Four Corners      
Public Utilities, Commitments And Contingencies [Line Items]      
Payments for relief from obligations 75,000,000    
Coal supply | NM Capital | San Juan Generating Station      
Public Utilities, Commitments And Contingencies [Line Items]      
Requirement to post reclamation bonds 118,700,000    
Cash used to support bank letter or credit arrangement 30,300,000    
Four Corners CSA | PNM      
Public Utilities, Commitments And Contingencies [Line Items]      
Funds contributed, mine reclamation trust   2,400,000  
Reclamation trust funding, remainder of year 200,000    
San Juan Generating Station | Loss on long-term purchase commitment | PNM      
Public Utilities, Commitments And Contingencies [Line Items]      
Annual funding post-term reclamation trust   $ 10,000,000  
Annual funding post-term reclamation trust, remainder of year 0    
Annual funding post-term reclamation trust, year one 0    
Annual funding post-term reclamation trust, year two 0    
San Juan Generating Station and Four Corners | Mine Reclamation Trust | PNM      
Public Utilities, Commitments And Contingencies [Line Items]      
Customer reclamation funding cost $ 100,000,000