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Pension and Other Postretirement Benefits - Schedule of Components of Net Periodic Benefit Cost (Income) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
PNM | Pension Plan      
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]      
Service cost $ 0 $ 0 $ 0
Interest cost 21,709 23,653 16,857
Expected return on plan assets (31,029) (29,196) (28,563)
Amortization of net loss 10,646 10,583 15,794
Amortization of prior service cost 0 0 0
Net periodic benefit cost 1,326 5,040 4,088
PNM | Other Postretirement Benefits      
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]      
Service cost 0 0 10
Interest cost 2,387 2,703 1,914
Expected return on plan assets (5,563) (4,969) (4,351)
Amortization of net loss 0 0 0
Curtailment loss 0 0 836
Net periodic benefit cost (3,176) (2,266) (1,591)
PNM | Executive Retirement Program      
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]      
Service cost 0 0 0
Interest cost 496 540 362
Amortization of net loss 200 152 327
Amortization of prior service cost 0 0 0
Net periodic benefit cost 696 692 689
TNMP | Pension Plan      
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]      
Service cost 0 0 0
Interest cost 2,214 2,402 1,720
Expected return on plan assets (2,749) (2,697) (2,472)
Amortization of net loss 556 439 932
Amortization of prior service cost 0 0 0
Settlement loss 0 0 1,033
Net periodic benefit cost 21 144 1,213
TNMP | Other Postretirement Benefits      
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]      
Service cost 21 21 38
Interest cost 385 425 307
Expected return on plan assets (515) (481) (418)
Amortization of net loss (642) (760) (520)
Curtailment loss 0 0  
Net periodic benefit cost (751) (795) (593)
TNMP | Executive Retirement Program      
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]      
Service cost 0 0 0
Interest cost 15 18 11
Amortization of net loss 0 0 0
Amortization of prior service cost 0 0 0
Net periodic benefit cost $ 15 $ 18 $ 11