Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Total PNMR Common Stockholders’ Equity	Common Stock	AOCI	Retained Earnings	Non- controlling Interest in Valencia	PNM	PNM Total PNMR Common Stockholders’ Equity	PNM Common Stock	PNM AOCI	PNM Retained Earnings	PNM Non- controlling Interest in Valencia	Texas-New Mexico Power Company	Texas-New Mexico Power Company Common Stock	Texas-New Mexico Power Company Paid-in Capital	Texas-New Mexico Power Company Retained Earnings
Beginning balance at Dec. 31, 2019	$ 1,741,750	$ 1,678,698	$ 1,150,552	$ (99,377)	$ 627,523	$ 63,052	$ 1,512,431	$ 1,449,379	$ 1,264,918	$ (99,055)	$ 283,516	$ 63,052
Beginning balance TNMP at Dec. 31, 2019													$ 754,627	$ 64	$ 614,166	$ 140,397
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings before subsidiary preferred stock dividends	50,162	42,493			42,493	7,669	37,416	29,747			29,747	7,669
Net earnings							29,747						23,266			23,266
Total other comprehensive income (loss)	6,796	6,796		6,796			8,063	8,063		8,063
Subsidiary preferred stock dividends	(264)	(264)			(264)
Dividends declared on preferred stock							(264)	(264)			(264)
Dividends declared on common stock	(24,493)	(24,493)			(24,493)		(40,654)	(40,654)			(40,654)		(18,439)			(18,439)
Proceeds from stock option exercise	24	24	24
Awards of common stock	(11,984)	(11,984)	(11,984)
Stock based compensation expense	5,230	5,230	5,230
Valencia’s transactions with its owner	(10,794)					(10,794)	(10,794)					(10,794)
Ending balance at Jun. 30, 2020	1,756,427	1,696,500	1,143,822	(92,581)	645,259	59,927	1,506,198	1,446,271	1,264,918	(90,992)	272,345	59,927
Ending balance TNMP at Jun. 30, 2020													759,454	64	614,166	145,224
Beginning balance at Mar. 31, 2020	1,687,569	1,627,222	1,142,879	(103,427)	587,770	60,347	1,450,484	1,390,137	1,264,918	(101,586)	226,805	60,347
Beginning balance TNMP at Mar. 31, 2020													750,372	64	614,166	136,142
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings before subsidiary preferred stock dividends	61,561	57,621			57,621	3,940	49,612	45,672			45,672	3,940
Net earnings							45,672						16,174			16,174
Total other comprehensive income (loss)	10,846	10,846		10,846			10,594	10,594		10,594
Subsidiary preferred stock dividends	(132)	(132)			(132)
Dividends declared on preferred stock							(132)	(132)			(132)
Dividends declared on common stock							(40,700)						(7,092)			(7,092)
Awards of common stock	(486)	(486)	(486)
Stock based compensation expense	1,429	1,429	1,429
Valencia’s transactions with its owner	(4,360)					(4,360)	(4,360)					(4,360)
Ending balance at Jun. 30, 2020	1,756,427	1,696,500	1,143,822	(92,581)	645,259	59,927	1,506,198	1,446,271	1,264,918	(90,992)	272,345	59,927
Ending balance TNMP at Jun. 30, 2020													759,454	64	614,166	145,224
Beginning balance at Dec. 31, 2020	2,108,474	2,049,465	1,429,941	(79,183)	698,707	59,009	1,863,752	1,804,743	1,494,918	(78,511)	388,336	59,009
Beginning balance TNMP at Dec. 31, 2020	2,049,465						1,804,743						825,678	64	685,166	140,448
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings before subsidiary preferred stock dividends	78,966	71,552			71,552	7,414	67,566	60,152			60,152	7,414
Net earnings							60,152						24,385			24,385
Total other comprehensive income (loss)	(170)	(170)		(170)			(842)	(842)		(842)
Equity contribution from parent													52,000		52,000
Subsidiary preferred stock dividends	(264)	(264)			(264)
Dividends declared on preferred stock							(264)	(264)			(264)
Dividends declared on common stock	(28,111)	(28,111)			(28,111)
Awards of common stock	(9,953)	(9,953)	(9,953)
Stock based compensation expense	5,712	5,712	5,712
Valencia’s transactions with its owner	(9,256)					(9,256)	(9,256)					(9,256)
Ending balance at Jun. 30, 2021	2,145,398	2,088,231	1,425,700	(79,353)	741,884	57,167	1,920,956	1,863,789	1,494,918	(79,353)	448,224	57,167
Ending balance TNMP at Jun. 30, 2021	2,088,231						1,863,789						902,063	64	737,166	164,833
Beginning balance at Mar. 31, 2021	2,088,226	2,030,966	1,425,133	(82,342)	688,175	57,260	1,876,916	1,819,656	1,494,918	(82,134)	406,872	57,260
Beginning balance TNMP at Mar. 31, 2021													834,413	64	685,166	149,183
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings before subsidiary preferred stock dividends	57,761	53,841			53,841	3,920	45,404	41,484			41,484	3,920
Net earnings							41,484						15,650			15,650
Total other comprehensive income (loss)	2,989	2,989		2,989			2,781	2,781		2,781
Equity contribution from parent													52,000		52,000
Subsidiary preferred stock dividends	(132)	(132)			(132)
Dividends declared on preferred stock							(132)	(132)			(132)
Awards of common stock	(926)	(926)	(926)
Stock based compensation expense	1,493	1,493	1,493
Valencia’s transactions with its owner	(4,013)					(4,013)	(4,013)					(4,013)
Ending balance at Jun. 30, 2021	2,145,398	$ 2,088,231	$ 1,425,700	$ (79,353)	$ 741,884	$ 57,167	1,920,956	$ 1,863,789	$ 1,494,918	$ (79,353)	$ 448,224	$ 57,167
Ending balance TNMP at Jun. 30, 2021	$ 2,088,231						$ 1,863,789						$ 902,063	$ 64	$ 737,166	$ 164,833