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Income Taxes (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2025
Dec. 31, 2025
Dec. 31, 2017
Income Tax Contingency [Line Items]      
Regulatory disallowances, tax effect $ 0.2    
Sale of equity method investee, tax effect 0.1    
Income tax assessment 0.1    
Deferred federal, state and local, income taxes $ 25.6    
Forecast      
Income Tax Contingency [Line Items]      
Effective tax rate   12.34%  
NMPRC      
Income Tax Contingency [Line Items]      
Period of time for proposed return to customers the benefit of the reduction in federal corporate income tax rate 4 years   23 years
Unprotected excess deferred income taxes $ 62.7    
PNM      
Income Tax Contingency [Line Items]      
Deferred federal, state and local, income taxes 22.9    
PNM | Forecast      
Income Tax Contingency [Line Items]      
Effective tax rate   10.42%  
TNMP      
Income Tax Contingency [Line Items]      
Deferred federal, state and local, income taxes $ 2.7    
TNMP | Forecast      
Income Tax Contingency [Line Items]      
Effective tax rate   20.21%