XML 163 R130.htm IDEA: XBRL DOCUMENT v3.25.0.1
Commitments and Contingencies - Coal Supply (Narrative) (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2024
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Jan. 31, 2016
Other Commitments [Line Items]          
Coal requirement, minimum required payment, year one   $ 42.5      
Coal requirement, minimum required payment, year two   85.9      
Public Utilities, Coal Requirement, Coal requirement, minimum required payment, year three   85.9      
Coal requirement, minimum required payment, year four   89.8      
Coal requirement, minimum required payment, year five   89.8      
Coal requirement, minimum required payment, after year five   71.0      
San Juan Generating Station          
Other Commitments [Line Items]          
Reclamation and mine shutdown provision $ 20.9 12.1      
Regulatory disallowance 4.0        
Other costs 0.5        
Underground | San Juan Generating Station          
Other Commitments [Line Items]          
Regulatory liabilities $ 17.0 6.0      
Surface | San Juan Generating Station          
Other Commitments [Line Items]          
Reclamation and mine shutdown provision   1.6      
Regulatory liabilities   6.1      
Reclamation, maximum collection from customers   100.0      
San Juan Generating Station | Coal Supply          
Other Commitments [Line Items]          
Issuance in letters of credit         $ 30.3
NM Capital | San Juan Generating Station | Coal Supply          
Other Commitments [Line Items]          
Coal mine reclamation bonds to be posted with NMMMD   118.7      
Issuance in letters of credit   30.3      
PNM | Loss on Long-Term Purchase Commitment | San Juan Generating Station          
Other Commitments [Line Items]          
Annual funding post-term reclamation trust   27.3 $ 2.7 $ 10.0  
PNM | Loss on Long-Term Purchase Commitment | San Juan Generating Station          
Other Commitments [Line Items]          
Public utilities, annual funding post-term reclamation trust, year one   1.0      
Public utilities, annual funding post-term reclamation trust, year two   0.6      
PNM | Four Corners CSA          
Other Commitments [Line Items]          
Funds contributed to mine reclamation trust   3.2 0.2 $ 2.4  
Reclamation trust funding, year one   0.5      
Reclamation trust funding, year two   0.5      
PNM | Mine Reclamation Trust | San Juan Generating Station and Four Corners          
Other Commitments [Line Items]          
Customer reclamation funding cost, maximum   100.0      
PNM | Underground | Loss on Long-Term Purchase Commitment          
Other Commitments [Line Items]          
Liability for interim storage costs   52.9 26.2    
PNM | Surface | Loss on Long-Term Purchase Commitment          
Other Commitments [Line Items]          
Liability for interim storage costs   38.3 $ 50.0    
PNM | San Juan Generating Station | Underground | Loss on Long-Term Purchase Commitment          
Other Commitments [Line Items]          
Estimate of possible loss   62.7      
PNM | San Juan Generating Station | Surface | Loss on Long-Term Purchase Commitment          
Other Commitments [Line Items]          
Estimate of possible loss   $ 51.1