Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 2,169,800	$ 2,088,226	$ 2,222,929	$ 2,108,474
Total Other Comprehensive Income (Loss)	(245)	2,989	(4,889)	(170)
Ending balance	2,185,687	2,145,398	2,185,687	2,145,398
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(76,580)	(82,342)	(71,936)	(79,183)
Amounts reclassified from AOCI (pre-tax)			(550)	(2,361)
Income tax impact of amounts reclassified			140	599
Other OCI changes (pre-tax)			(6,004)	2,133
Income tax impact of other OCI changes			1,525	(541)
Total Other Comprehensive Income (Loss)	(245)	2,989	(4,889)	(170)
Ending balance	(76,825)	(79,353)	(76,825)	(79,353)
Fair Value Adjustment for Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			0	(672)
Amounts reclassified from AOCI (pre-tax)			(1,185)	(903)
Income tax impact of amounts reclassified			301	229
Other OCI changes (pre-tax)			3,448	1,804
Income tax impact of other OCI changes			(876)	(458)
Total Other Comprehensive Income (Loss)			1,688	672
Ending balance	1,688	0	1,688	0
PNM
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	2,013,794	1,876,916	2,015,264	1,863,752
Total Other Comprehensive Income (Loss)	(1,933)	2,781	(6,577)	(842)
Ending balance	2,005,541	1,920,956	2,005,541	1,920,956
PNM | Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(76,580)	(82,134)	(71,936)	(78,511)
Amounts reclassified from AOCI (pre-tax)			635	(1,458)
Income tax impact of amounts reclassified			(161)	370
Other OCI changes (pre-tax)			(9,452)	329
Income tax impact of other OCI changes			2,401	(83)
Total Other Comprehensive Income (Loss)	(1,933)	2,781	(6,577)	(842)
Ending balance	(78,513)	(79,353)	(78,513)	(79,353)
PNM | Unrealized Gains on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			11,715	20,403
Amounts reclassified from AOCI (pre-tax)			(2,917)	(5,632)
Income tax impact of amounts reclassified			741	1,430
Other OCI changes (pre-tax)			(9,452)	329
Income tax impact of other OCI changes			2,401	(83)
Total Other Comprehensive Income (Loss)			(9,227)	(3,956)
Ending balance	2,488	16,447	2,488	16,447
PNM | Pension Liability Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(83,651)	(98,914)
Amounts reclassified from AOCI (pre-tax)			3,552	4,174
Income tax impact of amounts reclassified			(902)	(1,060)
Other OCI changes (pre-tax)			0	0
Income tax impact of other OCI changes			0	0
Total Other Comprehensive Income (Loss)			2,650	3,114
Ending balance	$ (81,001)	$ (95,800)	$ (81,001)	$ (95,800)