v3.26.3
Pension and Other Postretirement Benefit Plans - Schedule of Net Periodic Benefit Costs (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
PNM | Pension Plan        
Components of Net Periodic Benefit Cost        
Service cost $ 0 $ 0 $ 0 $ 0
Interest cost 3,822 5,385 11,466 16,154
Expected return on plan assets (5,608) (7,459) (16,825) (22,375)
Amortization of net loss 2,593 3,124 7,779 9,371
Amortization of prior service cost 0 0 0 0
Net Periodic Benefit Cost (Income) 807 1,050 2,420 3,150
PNM | OPEB Plan        
Components of Net Periodic Benefit Cost        
Service cost 0 0 0 0
Interest cost 537 567 1,611 1,700
Expected return on plan assets (1,349) (1,384) (4,048) (4,152)
Amortization of net loss 0 0 0 0
Amortization of prior service cost 0 0 0 0
Net Periodic Benefit Cost (Income) (812) (817) (2,437) (2,452)
PNM | Executive Retirement Program        
Components of Net Periodic Benefit Cost        
Service cost 0 0 0 0
Interest cost 103 121 309 365
Expected return on plan assets 0 0 0 0
Amortization of net loss 34 47 103 141
Amortization of prior service cost 0 0 0 0
Net Periodic Benefit Cost (Income) 137 168 412 506
Texas-New Mexico Power Company | Pension Plan        
Components of Net Periodic Benefit Cost        
Service cost 0 0 0 0
Interest cost 481 536 1,443 1,608
Expected return on plan assets (739) (733) (2,218) (2,199)
Amortization of net loss 210 168 631 504
Amortization of prior service cost 0 0 0 0
Net Periodic Benefit Cost (Income) (48) (29) (144) (87)
Texas-New Mexico Power Company | OPEB Plan        
Components of Net Periodic Benefit Cost        
Service cost 5 4 14 13
Interest cost 87 94 261 280
Expected return on plan assets (108) (120) (324) (361)
Amortization of net loss (89) (124) (266) (372)
Amortization of prior service cost 8 0 25 0
Net Periodic Benefit Cost (Income) $ (97) $ (146) $ (290) $ (440)