v3.26.3
Fair Value of Derivative and Other Financial Instruments - Schedule of Items Recorded and Presented by Level of Hierarchy (Details) - USD ($)
$ in Thousands
 9 Months Ended 12 Months Ended
Sep. 30, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investment securities $ 500,225 $ 505,655
Fair value of long-term debt 5,587,856 5,506,722
Carrying Amount    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of long-term debt 5,760,515 5,418,564
PNM    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available-for-sale debt securities 39,034  
Investments categorized within the fair value hierarchy 401,294 427,604
Real estate funds 39,402 20,307
Hedge funds 14,334 12,600
Investment securities 500,225 505,655
Unrealized Gains 27 329
Fair value of long-term debt 2,811,838 2,757,316
PNM | Carrying Amount    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of long-term debt 3,054,817 2,861,897
PNM | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments categorized within the fair value hierarchy 398,924 421,873
PNM | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments categorized within the fair value hierarchy 2,370 5,731
Texas-New Mexico Power Company    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of long-term debt 1,697,097 1,662,457
Texas-New Mexico Power Company | Carrying Amount    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of long-term debt 1,821,527 1,672,267
Cash and cash equivalents | PNM    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and cash equivalents 10,564 33,469
Cash and cash equivalents | PNM | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and cash equivalents 10,564 33,469
Cash and cash equivalents | PNM | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and cash equivalents 0 0
Corporate stocks, common | PNM    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity securities: 127,579 154,790
Corporate stocks, common | PNM | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity securities: 127,579 154,790
Corporate stocks, common | PNM | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity securities: 0 0
Mutual funds and other | PNM    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity securities: 224,117 202,995
Mutual funds and other | PNM | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity securities: 224,117 202,995
Mutual funds and other | PNM | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity securities: 0 0
U.S. government | PNM    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available-for-sale debt securities 36,664 30,619
Unrealized Gains 12 227
U.S. government | PNM | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available-for-sale debt securities 36,664 30,619
U.S. government | PNM | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available-for-sale debt securities 0 0
Corporate and other | PNM    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available-for-sale debt securities 2,370 5,731
Unrealized Gains 15 102
Corporate and other | PNM | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available-for-sale debt securities 0 0
Corporate and other | PNM | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Available-for-sale debt securities 2,370 5,731
Uncategorized collective investment trust | PNM    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Other investments $ 45,195 $ 45,144