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Commitments and Contingencies - PVNGS Liability and Insurance Matters, Navajo Nation Allottee Matters and Texas Winter Storm (Details)
 1 Months Ended 3 Months Ended
Sep. 30, 2012
landowner
Mar. 31, 2022
USD ($)
generating_unit
Dec. 31, 2021
USD ($)
Dec. 01, 2015
Allotment_Parcel
Jul. 13, 2015
a
Jan. 22, 2015
Allotment_Parcel
PNM | Navajo Nation Allottee Matters            
Public Utilities, Commitments And Contingencies [Line Items]            
Number of landowners involved in the appeal | landowner 43          
Number of allotments where landowners are revoking rights of way renewal consents (in allotment parcels) | Allotment_Parcel       2   10
Area of land (in acres) | a         15.49  
Number of allotment parcels at issue that are not to be condemned | Allotment_Parcel       2    
Number of allotment parcels at issue | Allotment_Parcel       5    
PNM | Palo Verde Nuclear Generating Station | Nuclear plant            
Public Utilities, Commitments And Contingencies [Line Items]            
Ownership percentage in nuclear reactor   10.20%        
Number of units | generating_unit   3        
Maximum potential assessment per incident   $ 42,100,000        
Annual payment limitation related to incident   6,200,000        
Aggregate amount of all risk insurance   2,800,000,000        
Maximum amount under Nuclear Electric Insurance Limited   5,400,000        
PNM | Maximum | Palo Verde Nuclear Generating Station | Nuclear plant            
Public Utilities, Commitments And Contingencies [Line Items]            
Liability insurance coverage   13,500,000,000        
Liability insurance coverage sublimit   2,250,000,000        
Texas-New Mexico Power Company            
Public Utilities, Commitments And Contingencies [Line Items]            
Regulatory assets   800,000 $ 800,000      
Commercial providers | PNM | Palo Verde Nuclear Generating Station | Nuclear plant            
Public Utilities, Commitments And Contingencies [Line Items]            
Liability insurance coverage   450,000,000        
Industry Wide Retrospective Assessment Program | PNM | Palo Verde Nuclear Generating Station | Nuclear plant            
Public Utilities, Commitments And Contingencies [Line Items]            
Liability insurance coverage   $ 13,100,000,000