Segment Information - Summarized Financial Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) segment	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	Apr. 01, 2018 USD ($)
Segment Reporting Information, Profit (Loss) [Abstract]
Electric operating revenues	$ 729,888	$ 554,551	$ 1,673,736	$ 1,345,798
Utility margin	269,221	237,097	593,647	520,664
Other operating expenses	136,216	132,004	409,061	397,209
Depreciation and amortization	76,570	71,438	229,103	212,039
Operating income	182,763	151,729	337,223	269,098
Interest income (expense)	3,969	3,329	11,588	10,466
Other income (deductions)	(12,019)	2,536	(76,788)	16,864
Interest Charges	(34,526)	(23,244)	(89,963)	(73,247)
Earnings before Income Taxes	140,187	134,350	182,060	223,181
Income taxes (benefit)	13,450	16,668	16,982	26,533
Net Earnings	126,737	117,682	165,078	196,648
Valencia non-controlling interest	(4,172)	(4,229)	(10,897)	(11,643)
Subsidiary preferred stock dividends	(132)	(132)	(396)	(396)
Net Earnings Available for PNM Common Stock	122,433	113,321	153,785	184,609
Total Assets	9,028,890	8,256,070	9,028,890	8,256,070	$ 8,666,885
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	597,337	435,523	$ 1,312,800	1,030,685
Depreciation and amortization	45,361	42,673	137,132	127,111
Operating income	139,915	114,563	234,366	199,380
Interest Charges	(15,467)	(12,509)	(44,562)	(38,441)
Earnings before Income Taxes	113,893	106,776	118,617	185,020
Income taxes (benefit)	12,121	15,500	11,762	26,178
Net Earnings	101,772	91,276	106,855	158,842
Valencia non-controlling interest	(4,172)	(4,229)	(10,897)	(11,643)
Subsidiary preferred stock dividends	(132)	(132)	(396)	(396)
Net Earnings Available for PNM Common Stock	97,468	86,915	95,562	146,803
Total Assets	6,113,416		6,113,416		6,060,133
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	132,551	119,028	$ 360,936	315,113
Cost of energy	30,988	28,478	92,220	83,896
Depreciation and amortization	24,960	23,031	72,914	67,696
Operating income	43,837	38,842	106,079	80,571
Interest Charges	(9,851)	(8,403)	(28,017)	(25,155)
Earnings before Income Taxes	36,377	31,583	83,800	58,667
Income taxes (benefit)	4,946	3,642	11,258	6,341
Net Earnings			72,542	52,326
Total Assets	2,673,546		2,673,546		2,364,772
Goodwill	226,665		226,665		$ 226,665	$ 226,700
PNM
Segment Reporting Information, Profit (Loss) [Abstract]
Utility margin	201,607	176,730	421,327	378,403
Other operating expenses	108,710	107,385	335,173	320,638
Depreciation and amortization	45,361	42,673	137,132	127,111
Operating income	139,915	114,563	234,366	199,380
Interest income (expense)	3,888	3,364	10,288	10,376
Other income (deductions)	(14,443)	1,358	(81,475)	13,705
Interest Charges	(15,467)	(12,509)	(44,562)	(38,441)
Earnings before Income Taxes	113,893	106,776	118,617	185,020
Income taxes (benefit)	12,121	15,500	11,762	26,178
Net Earnings	101,772	91,276	106,855	158,842
Valencia non-controlling interest	(4,172)	(4,229)	(10,897)	(11,643)
Subsidiary preferred stock dividends	(132)	(132)	(396)	(396)
Net Earnings Available for PNM Common Stock	97,468	86,915	95,562	146,803
Total Assets	6,113,416	5,723,176	6,113,416	5,723,176
Goodwill	51,632	51,632	51,632	51,632
TNMP
Segment Reporting Information, Profit (Loss) [Abstract]
Utility margin	67,614	60,367	172,320	142,261
Other operating expenses	32,766	28,677	89,723	82,950
Depreciation and amortization	24,960	23,031	72,914	67,696
Operating income	43,837	38,842	106,079	80,571
Interest income (expense)	148	0	1,435	0
Other income (deductions)	2,243	1,144	4,303	3,251
Interest Charges	(9,851)	(8,403)	(28,017)	(25,155)
Earnings before Income Taxes	36,377	31,583	83,800	58,667
Income taxes (benefit)	4,946	3,642	11,258	6,341
Net Earnings	31,431	27,941	72,542	52,326
Valencia non-controlling interest	0	0	0	0
Subsidiary preferred stock dividends	0	0	0	0
Net Earnings Available for PNM Common Stock	31,431	27,941	72,542	52,326
Total Assets	2,673,546	2,311,559	2,673,546	2,311,559
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	(5,260)	(4,058)	(15,835)	(6,379)
Depreciation and amortization	6,249	5,734	19,057	17,232
Operating income	(989)	(1,676)	(3,222)	(10,853)
Interest income (expense)	(67)	(35)	(135)	90
Other income (deductions)	181	34	384	(92)
Interest Charges	(9,208)	(2,332)	(17,384)	(9,651)
Earnings before Income Taxes	(10,083)	(4,009)	(20,357)	(20,506)
Income taxes (benefit)	(3,617)	(2,474)	(6,038)	(5,986)
Net Earnings	(6,466)	(1,535)	(14,319)	(14,520)
Valencia non-controlling interest	0	0	0	0
Subsidiary preferred stock dividends	0	0	0	0
Net Earnings Available for PNM Common Stock	(6,466)	(1,535)	(14,319)	(14,520)
Total Assets	241,928	221,335	241,928	221,335
Goodwill	0	0	0	0
Energy
Segment Reporting Information, Profit (Loss) [Abstract]
Electric operating revenues	729,888	554,551	1,673,736	1,345,798
Cost of energy	334,339	199,380	698,349	467,452
Utility margin	395,549	355,171	975,387	878,346
Energy | PNM
Segment Reporting Information, Profit (Loss) [Abstract]
Cost of energy	303,351	170,902	606,129	383,556
Energy | PNM
Segment Reporting Information, Profit (Loss) [Abstract]
Electric operating revenues	597,337	435,523	1,312,800	1,030,685
Cost of energy	303,351	170,902	606,129	383,556
Utility margin	293,986	264,621	706,671	647,129
Energy | TNMP
Segment Reporting Information, Profit (Loss) [Abstract]
Electric operating revenues	132,551	119,028	360,936	315,113
Cost of energy	30,988	28,478	92,220	83,896
Utility margin	101,563	90,550	268,716	231,217
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