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Regulatory and Rate Matters - Four Corners Abandonment Application (Details) - Four Corners - PNM - USD ($)
$ in Millions
 1 Months Ended 12 Months Ended
Jan. 08, 2021
Nov. 01, 2020
Nov. 30, 2020
Dec. 31, 2023
Public Utilities, General Disclosures [Line Items]        
Payments for relief from obligations   $ 75.0 $ 15.0  
Final payment for relief from obligations     $ 60.0  
Request issuance of energy transition bonds $ 300.0      
Forecasted undepreciated investment 272.0      
Plant decommissioning and coal mine reclamation costs 4.6      
Upfront financing costs 7.3      
Proceeds from securitization bonds $ 16.5      
Regulatory disallowance       $ 3.7
PNM        
Public Utilities, General Disclosures [Line Items]        
Ownership percentage by noncontrolling owners   13.00%