Pension and Other Postretirement Benefit Plans - Schedule of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
PNM | Pension Plan
Components of Net Periodic Benefit Cost
Service cost	$ 0	$ 0
Interest cost	5,427	5,913
Expected return on plan assets	(7,757)	(7,299)
Amortization of net loss	2,661	2,646
Amortization of prior service cost	0	0
Net Periodic Benefit Cost (Income)	331	1,260
PNM | OPEB Plan
Components of Net Periodic Benefit Cost
Service cost	0	0
Interest cost	597	676
Expected return on plan assets	(1,391)	(1,243)
Amortization of net loss	0	0
Amortization of prior service cost	0	0
Net Periodic Benefit Cost (Income)	(794)	(567)
PNM | Executive Retirement Program
Components of Net Periodic Benefit Cost
Service cost	0	0
Interest cost	124	135
Expected return on plan assets	0	0
Amortization of net loss	50	38
Amortization of prior service cost	0	0
Net Periodic Benefit Cost (Income)	174	173
Texas-New Mexico Power Company | Pension Plan
Components of Net Periodic Benefit Cost
Service cost	0	0
Interest cost	553	601
Expected return on plan assets	(687)	(674)
Amortization of net loss	139	110
Amortization of prior service cost	0	0
Net Periodic Benefit Cost (Income)	5	37
Texas-New Mexico Power Company | OPEB Plan
Components of Net Periodic Benefit Cost
Service cost	5	5
Interest cost	96	106
Expected return on plan assets	(129)	(120)
Amortization of net loss	(161)	(190)
Amortization of prior service cost	0	0
Net Periodic Benefit Cost (Income)	(189)	(199)
Texas-New Mexico Power Company | Executive Retirement Program
Components of Net Periodic Benefit Cost
Service cost	0	0
Interest cost	4	3
Expected return on plan assets	0	0
Amortization of net loss	0	0
Amortization of prior service cost	0	0
Net Periodic Benefit Cost (Income)	$ 4	$ 3