Electric Operating Revenues - Disaggregation of revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	$ 531,966	$ 481,881	$ 1,320,779	$ 1,197,359
Alternative revenue programs	(11,643)	(9,483)	(14,569)	(3,156)
Other electric operating revenue	209,565	82,153	367,526	151,595
Revenues	729,888	554,551	1,673,736	1,345,798
PNM
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	388,371	361,701	944,235	884,559
Alternative revenue programs	(599)	(8,331)	1,039	(5,469)
Other electric operating revenue	209,565	82,153	367,526	151,595
Revenues	597,337	435,523	1,312,800	1,030,685
TNMP
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	143,595	120,180	376,544	312,800
Alternative revenue programs	(11,044)	(1,152)	(15,608)	2,313
Other electric operating revenue	0	0	0	0
Revenues	132,551	119,028	360,936	315,113
Energy
Disaggregation of Revenue [Line Items]
Revenues	729,888	554,551	1,673,736	1,345,798
Energy | Residential
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	211,560	206,874	514,526	499,394
Energy | Commercial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	178,019	171,505	436,857	420,422
Energy | Industrial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	35,059	32,138	95,739	88,214
Energy | Public authority
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	8,613	9,002	20,869	21,873
Energy | Economy energy service
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	11,784	7,389	31,726	24,722
Energy | PNM | Residential
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	150,682	155,035	368,159	377,794
Energy | PNM | Commercial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	136,314	137,071	325,492	327,090
Energy | PNM | Industrial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	25,609	24,856	68,351	66,593
Energy | PNM | Public authority
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	6,893	7,388	16,063	17,312
Energy | PNM | Economy energy service
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	11,784	7,389	31,726	24,722
Energy | TNMP | Residential
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	60,878	51,839	146,367	121,600
Energy | TNMP | Commercial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	41,705	34,434	111,365	93,332
Energy | TNMP | Industrial
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	9,450	7,282	27,388	21,621
Energy | TNMP | Public authority
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	1,720	1,614	4,806	4,561
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	73,394	50,534	198,430	129,768
Transmission | PNM
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	44,513	26,459	114,699	60,919
Transmission | TNMP
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	28,881	24,075	83,731	68,849
Miscellaneous
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	13,537	4,439	22,632	12,966
Miscellaneous | PNM
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	12,576	3,503	19,745	10,129
Miscellaneous | TNMP
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	$ 961	$ 936	$ 2,887	$ 2,837