Pension and Other Postretirement Benefit Plans - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pension Plan | PNM
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			$ 0	$ 0
Estimated employer contributions for remainder of fiscal year through year four	$ 0		0
Estimated future contributions, year five	400,000		$ 400,000
Pension Plan | PNM | Maximum
Defined Benefit Plan Disclosure [Line Items]
Assumptions used calculating net periodic benefit cost, discount rate			5.70%
Pension Plan | Texas-New Mexico Power Company
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			$ 0	0
Estimated employer contributions for remainder of fiscal year through year four	0		$ 0
Pension Plan | Texas-New Mexico Power Company | Maximum
Defined Benefit Plan Disclosure [Line Items]
Assumptions used calculating net periodic benefit cost, discount rate			5.80%
OPEB Plan | PNM
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			$ 0	0
Disbursements by employer	100,000	$ 900,000	100,000	2,400,000
Disbursements by employer, year one through four			9,000,000
Estimated disbursement by employer, current year			200,000
OPEB Plan | Texas-New Mexico Power Company
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	0	0	0	0
Disbursements by employer, year one through four			0
Executive Retirement Program | PNM
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	400,000	400,000	1,000,000	1,000,000
Disbursements by employer, year one through four			4,500,000
Estimated disbursement by employer, current year			1,300,000
Executive Retirement Program | Texas-New Mexico Power Company
Defined Benefit Plan Disclosure [Line Items]
Disbursements by employer, year one through four			200,000
Estimated disbursement by employer, current year			100,000
Executive Retirement Program | Texas-New Mexico Power Company | Maximum
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 0	$ 0	$ 0	$ 0