Pension and Other Postretirement Benefit Plans - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 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
Pension Plan | PNM | Maximum
Defined Benefit Plan Disclosure [Line Items]
Assumptions used calculating net periodic benefit cost, discount rate			2.90%
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			2.90%
OPEB Plan | PNM
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			$ 0	0
Disbursements by employer	900,000	$ 800,000	1,800,000	1,700,000
Disbursements by employer, year one through four	11,900,000		11,900,000
Estimated disbursement by employer, current year			3,200,000
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		0
Executive Retirement Program | PNM
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	300,000	$ 300,000	600,000	800,000
Disbursements by employer, year one through four	4,700,000		4,700,000
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	$ 300,000		300,000
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