Pension and Other Postretirement Benefit Plans - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
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	600,000		$ 600,000
Pension Plan | PNM | Maximum
Defined Benefit Plan Disclosure [Line Items]
Assumptions used calculating net periodic benefit cost, discount rate			5.00%
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			5.00%
OPEB Plan | PNM
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			$ 0	0
Disbursements by employer	900,000	$ 1,000,000	2,400,000	2,700,000
Disbursements by employer, year one through four	15,100,000		15,100,000
Estimated disbursement by employer, current year			3,400,000
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		0
Executive Retirement Program | PNM
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	400,000	$ 300,000	1,000,000	1,100,000
Disbursements by employer, year one through four	5,800,000		5,800,000
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		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			$ 100,000	$ 100,000