Segment Information - Summarized Financial Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) segment	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)	Apr. 01, 2020 USD ($)	Apr. 01, 2018 USD ($)
Segment Reporting Information, Profit (Loss) [Abstract]
Electric operating revenues	$ 505,851	$ 729,888	$ 1,527,084	$ 1,673,736
Utility margin	177,178	269,221	545,516	593,647
Other operating expenses	128,694	136,216	387,155	409,061
Depreciation and amortization	80,192	76,570	237,405	229,103
Operating income	86,652	182,763	278,073	337,223
Interest income (expense)	5,366	3,969	15,568	11,588
Other income	(4,531)	(12,019)	8,374	(76,788)
Interest Charges	(49,838)	(34,526)	(136,660)	(89,963)
Earnings before Income Taxes	37,649	140,187	165,355	182,060
Income taxes (benefit)	(5,267)	13,450	12,742	16,982
Net Earnings	42,916	126,737	152,613	165,078
Valencia non-controlling interest	(5,058)	(4,172)	(14,172)	(10,897)
Subsidiary preferred stock dividends	(132)	(132)	(396)	(396)
Net Earnings Available for PNM Common Stock	37,726	122,433	138,045	153,785
Total Assets	10,050,841	9,028,890	10,050,841	9,028,890	$ 9,257,377
Goodwill	278,297	278,297	$ 278,297	278,297	278,297
PNM
Segment Reporting Information [Line Items]
Number of operating segments | segment			1
Segment Reporting Information, Profit (Loss) [Abstract]
Electric operating revenues	350,334	597,337	$ 1,118,741	1,312,800
Depreciation and amortization	44,537	45,361	132,287	137,132
Operating income	30,696	139,915	163,015	234,366
Interest Charges	(22,354)	(15,467)	(61,242)	(44,562)
Earnings before Income Taxes	6,067	113,893	120,445	118,617
Income taxes (benefit)	(7,199)	12,121	12,041	11,762
Net Earnings	13,266	101,772	108,404	106,855
Valencia non-controlling interest	(5,058)	(4,172)	(14,172)	(10,897)
Subsidiary preferred stock dividends	(132)	(132)	(396)	(396)
Net Earnings Available for PNM Common Stock	8,076	97,468	93,836	95,562
Total Assets	6,731,852		6,731,852		6,272,166
Goodwill	51,632		$ 51,632		51,632		$ 51,600
TNMP
Segment Reporting Information [Line Items]
Number of operating segments | segment			1
Segment Reporting Information, Profit (Loss) [Abstract]
Electric operating revenues	155,517	132,551	$ 408,343	360,936
Cost of energy	35,951	30,988	106,627	92,220
Depreciation and amortization	28,357	24,960	83,746	72,914
Operating income	56,154	43,837	116,668	106,079
Interest Charges	(12,095)	(9,851)	(33,932)	(28,017)
Earnings before Income Taxes	46,685	36,377	87,245	83,800
Income taxes (benefit)	7,181	4,946	13,076	11,258
Net Earnings			74,169	72,542
Total Assets	3,039,357		3,039,357		2,746,601
Goodwill	226,665		226,665		$ 226,665	$ 226,700
PNM
Segment Reporting Information, Profit (Loss) [Abstract]
Utility margin	95,721	201,607	356,317	421,327
Other operating expenses	100,739	108,710	305,615	335,173
Depreciation and amortization	44,537	45,361	132,287	137,132
Operating income	30,696	139,915	163,015	234,366
Interest income (expense)	5,323	3,888	15,542	10,288
Other income	(7,598)	(14,443)	3,130	(81,475)
Interest Charges	(22,354)	(15,467)	(61,242)	(44,562)
Earnings before Income Taxes	6,067	113,893	120,445	118,617
Income taxes (benefit)	(7,199)	12,121	12,041	11,762
Net Earnings	13,266	101,772	108,404	106,855
Valencia non-controlling interest	(5,058)	(4,172)	(14,172)	(10,897)
Subsidiary preferred stock dividends	(132)	(132)	(396)	(396)
Net Earnings Available for PNM Common Stock	8,076	97,468	93,836	95,562
Total Assets	6,731,852	6,113,416	6,731,852	6,113,416
Goodwill	51,632	51,632	51,632	51,632
TNMP
Segment Reporting Information, Profit (Loss) [Abstract]
Utility margin	81,457	67,614	189,199	172,320
Other operating expenses	35,055	32,766	101,302	89,723
Depreciation and amortization	28,357	24,960	83,746	72,914
Operating income	56,154	43,837	116,668	106,079
Interest income (expense)	178	148	413	1,435
Other income	2,448	2,243	4,096	4,303
Interest Charges	(12,095)	(9,851)	(33,932)	(28,017)
Earnings before Income Taxes	46,685	36,377	87,245	83,800
Income taxes (benefit)	7,181	4,946	13,076	11,258
Net Earnings	39,504	31,431	74,169	72,542
Valencia non-controlling interest	0	0	0	0
Subsidiary preferred stock dividends	0	0	0	0
Net Earnings Available for PNM Common Stock	39,504	31,431	74,169	72,542
Total Assets	3,039,357	2,673,546	3,039,357	2,673,546
Goodwill	226,665	226,665	226,665	226,665
Corporate and Other
Segment Reporting Information, Profit (Loss) [Abstract]
Utility margin	0	0	0	0
Other operating expenses	(7,100)	(5,260)	(19,762)	(15,835)
Depreciation and amortization	7,298	6,249	21,372	19,057
Operating income	(198)	(989)	(1,610)	(3,222)
Interest income (expense)	(135)	(67)	(387)	(135)
Other income	619	181	1,148	384
Interest Charges	(15,389)	(9,208)	(41,486)	(17,384)
Earnings before Income Taxes	(15,103)	(10,083)	(42,335)	(20,357)
Income taxes (benefit)	(5,249)	(3,617)	(12,375)	(6,038)
Net Earnings	(9,854)	(6,466)	(29,960)	(14,319)
Valencia non-controlling interest	0	0	0	0
Subsidiary preferred stock dividends	0	0	0	0
Net Earnings Available for PNM Common Stock	(9,854)	(6,466)	(29,960)	(14,319)
Total Assets	279,632	241,928	279,632	241,928
Goodwill	0	0	0	0
Energy
Segment Reporting Information, Profit (Loss) [Abstract]
Electric operating revenues	505,851	729,888	1,527,084	1,673,736
Cost of energy	210,313	334,339	624,451	698,349
Utility margin	295,538	395,549	902,633	975,387
Energy | PNM
Segment Reporting Information, Profit (Loss) [Abstract]
Cost of energy	174,362	303,351	517,824	606,129
Energy | PNM
Segment Reporting Information, Profit (Loss) [Abstract]
Electric operating revenues	350,334	597,337	1,118,741	1,312,800
Cost of energy	174,362	303,351	517,824	606,129
Utility margin	175,972	293,986	600,917	706,671
Energy | TNMP
Segment Reporting Information, Profit (Loss) [Abstract]
Electric operating revenues	155,517	132,551	408,343	360,936
Cost of energy	35,951	30,988	106,627	92,220
Utility margin	119,566	101,563	301,716	268,716
Energy | Corporate and Other
Segment Reporting Information, Profit (Loss) [Abstract]
Electric operating revenues	0	0	0	0
Cost of energy	0	0	0	0
Utility margin	$ 0	$ 0	$ 0	$ 0