Electric Operating Revenues - Disaggregation of revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	$ 509,923	$ 740,978	$ 1,503,056	$ 1,670,631
Alternative revenue programs	(4,977)	(11,643)	12,249	(14,569)
Other electric operating revenue	905	553	11,779	17,674
Electric Operating Revenues	505,851	729,888	1,527,084	1,673,736
PNM
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	350,368	597,383	1,096,999	1,294,087
Alternative revenue programs	(939)	(599)	9,963	1,039
Other electric operating revenue	905	553	11,779	17,674
Electric Operating Revenues	350,334	597,337	1,118,741	1,312,800
TNMP
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	159,555	143,595	406,057	376,544
Alternative revenue programs	(4,038)	(11,044)	2,286	(15,608)
Other electric operating revenue	0	0	0	0
Electric Operating Revenues	155,517	132,551	408,343	360,936
Energy
Disaggregation of Revenue [Line Items]
Electric Operating Revenues	505,851	729,888	1,527,084	1,673,736
Energy | Residential
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	180,962	211,561	486,720	514,526
Energy | Commercial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	147,899	178,019	423,917	436,857
Energy | Industrial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	30,556	35,059	101,883	95,739
Energy | Public authority
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	7,807	8,613	20,818	20,869
Energy | Economy energy service
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	4,958	11,784	24,999	31,726
Energy | PNM | Residential
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	111,406	150,683	339,307	368,159
Energy | PNM | Commercial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	106,237	136,314	309,560	325,492
Energy | PNM | Industrial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	19,891	25,609	65,524	68,351
Energy | PNM | Public authority
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	6,099	6,893	15,822	16,063
Energy | PNM | Economy energy service
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	4,958	11,784	24,999	31,726
Energy | TNMP | Residential
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	69,556	60,878	147,413	146,367
Energy | TNMP | Commercial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	41,662	41,705	114,357	111,365
Energy | TNMP | Industrial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	10,665	9,450	36,359	27,388
Energy | TNMP | Public authority
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	1,708	1,720	4,996	4,806
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	72,446	73,394	224,496	198,430
Transmission | PNM
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	37,466	44,513	124,396	114,699
Transmission | TNMP
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	34,980	28,881	100,100	83,731
Wholesale energy sales
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	62,804	220,219	213,098	365,554
Wholesale energy sales | PNM
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	62,804	220,219	213,098	365,554
Wholesale energy sales | TNMP
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	0
Miscellaneous
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	2,491	2,329	7,125	6,930
Miscellaneous | PNM
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	1,507	1,368	4,293	4,043
Miscellaneous | TNMP
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	$ 984	$ 961	$ 2,832	$ 2,887