Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 2,185,687	$ 2,145,398	$ 2,222,929	$ 2,108,474
Total Other Comprehensive Income (Loss)	6,646	(1,267)	1,757	(1,437)
Ending balance	2,255,728	2,201,364	2,255,728	2,201,364
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(76,825)	(79,353)	(71,936)	(79,183)
Amounts reclassified from AOCI (pre-tax)			135	(2,762)
Income tax impact of amounts reclassified			(34)	701
Other OCI changes (pre-tax)			2,221	836
Income tax impact of other OCI changes			(565)	(212)
Total Other Comprehensive Income (Loss)	6,646	(1,267)	1,757	(1,437)
Ending balance	(70,179)	(80,620)	(70,179)	(80,620)
Fair Value Adjustment for Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			0	(672)
Amounts reclassified from AOCI (pre-tax)			(1,767)	(903)
Income tax impact of amounts reclassified			449	229
Other OCI changes (pre-tax)			10,391	1,804
Income tax impact of other OCI changes			(2,640)	(458)
Total Other Comprehensive Income (Loss)			6,433	672
Ending balance	6,433	0	6,433	0
PNM
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	2,005,541	1,920,956	2,015,264	1,863,752
Total Other Comprehensive Income (Loss)	1,901	(1,267)	(4,676)	(2,109)
Ending balance	2,019,592	1,945,851	2,019,592	1,945,851
PNM | Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(78,513)	(79,353)	(71,936)	(78,511)
Amounts reclassified from AOCI (pre-tax)			1,902	(1,859)
Income tax impact of amounts reclassified			(483)	472
Other OCI changes (pre-tax)			(8,170)	(968)
Income tax impact of other OCI changes			2,075	246
Total Other Comprehensive Income (Loss)	1,901	(1,267)	(4,676)	(2,109)
Ending balance	(76,612)	(80,620)	(76,612)	(80,620)
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)			(3,426)	(8,120)
Income tax impact of amounts reclassified			870	2,062
Other OCI changes (pre-tax)			(8,170)	(968)
Income tax impact of other OCI changes			2,075	246
Total Other Comprehensive Income (Loss)			(8,651)	(6,780)
Ending balance	3,064	13,623	3,064	13,623
PNM | Pension Liability Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(83,651)	(98,914)
Amounts reclassified from AOCI (pre-tax)			5,328	6,261
Income tax impact of amounts reclassified			(1,353)	(1,590)
Other OCI changes (pre-tax)			0	0
Income tax impact of other OCI changes			0	0
Total Other Comprehensive Income (Loss)			3,975	4,671
Ending balance	$ (79,676)	$ (94,243)	$ (79,676)	$ (94,243)