Electric Operating Revenues - Disaggregation of revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	$ 404,320	$ 368,893	$ 788,813	$ 715,478
Alternative revenue programs	2,579	7,236	(2,926)	6,327
Other electric operating revenue	92,831	50,411	157,961	69,442
Revenues	499,730	426,540	943,848	791,247
PNM
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	280,220	271,652	555,864	522,858
Alternative revenue programs	3,703	1,886	1,638	2,862
Other electric operating revenue	92,831	50,411	157,961	69,442
Revenues	376,754	323,949	715,463	595,162
TNMP
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	124,100	97,241	232,949	192,620
Alternative revenue programs	(1,124)	5,350	(4,564)	3,465
Other electric operating revenue	0	0	0	0
Revenues	122,976	102,591	228,385	196,085
Energy
Disaggregation of Revenue [Line Items]
Revenues	499,730	426,540	943,848	791,247
Energy | Residential
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	151,023	142,757	302,966	292,519
Energy | Commercial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	137,731	137,554	258,838	248,917
Energy | Industrial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	29,158	29,883	60,680	56,077
Energy | Public authority
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	6,305	6,802	12,256	12,872
Energy | Economy energy service
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	11,003	6,753	19,943	17,334
Energy | PNM | Residential
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	104,902	108,090	217,477	222,759
Energy | PNM | Commercial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	101,174	108,085	189,178	190,019
Energy | PNM | Industrial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	19,610	22,837	42,742	41,737
Energy | PNM | Public authority
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	4,744	5,337	9,170	9,924
Energy | PNM | Economy energy service
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	11,003	6,753	19,943	17,334
Energy | TNMP | Residential
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	46,121	34,667	85,489	69,760
Energy | TNMP | Commercial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	36,557	29,469	69,660	58,898
Energy | TNMP | Industrial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	9,548	7,046	17,938	14,340
Energy | TNMP | Public authority
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	1,561	1,465	3,086	2,948
Energy | TNMP | Economy energy service
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Transmission
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	64,980	40,610	125,036	79,234
Transmission | PNM
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	35,659	16,957	70,186	34,460
Transmission | TNMP
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	29,321	23,653	54,850	44,774
Miscellaneous
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	4,120	4,534	9,094	8,525
Miscellaneous | PNM
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	3,128	3,593	7,168	6,625
Miscellaneous | TNMP
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	$ 992	$ 941	$ 1,926	$ 1,900