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, 2017	$ 1,761,448	$ 1,695,253	$ 1,157,665	$ (95,940)	$ 633,528	$ 66,195	$ 1,488,369	$ 1,422,174	$ 1,264,918	$ (97,093)	$ 254,349	$ 66,195
Beginning balance TNMP at Dec. 31, 2017													$ 634,405	$ 64	$ 504,166	$ 130,175
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) before subsidiary preferred stock dividends	61,248	53,462			53,462	7,786	42,296	34,510			34,510	7,786
Net earnings							34,510						24,779			24,779
Total other comprehensive income	3,391	3,391		3,391			1,592	1,592		1,592
Subsidiary preferred stock dividends	(264)	(264)			(264)
Dividends declared on preferred stock							(264)	(264)			(264)
Dividends declared on common stock	(21,108)	(21,108)			(21,108)								(10,436)			(10,436)
Proceeds from stock option exercise	924	924	924
Awards of common stock	(12,268)	(12,268)	(12,268)
Stock based compensation expense	3,325	3,325	3,325
Valencia’s transactions with its owner	(8,381)					(8,381)	(8,381)					(8,381)
Ending balance at Jun. 30, 2018	1,788,315	1,722,715	1,149,646	(103,757)	676,826	65,600	1,523,612	1,458,012	1,264,918	(106,709)	299,803	65,600
Ending balance TNMP at Jun. 30, 2018													648,748	64	504,166	144,518
Beginning balance at Mar. 31, 2018	1,749,014	1,683,614	1,150,516	(105,520)	638,618	65,400	1,495,561	1,430,161	1,264,918	(108,019)	273,262	65,400
Beginning balance TNMP at Mar. 31, 2018													642,794	64	504,166	138,564
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) before subsidiary preferred stock dividends	42,449	38,340			38,340	4,109	30,781	26,673			26,673	4,108
Net earnings							26,672						15,367			15,367
Total other comprehensive income	1,763	1,763		1,763			1,310	1,310		1,310
Subsidiary preferred stock dividends	(132)	(132)			(132)
Dividends declared on preferred stock							(132)	(132)			(132)
Dividends declared on common stock													(9,413)			(9,413)
Proceeds from stock option exercise	122	122	122
Awards of common stock	(1,423)	(1,423)	(1,423)
Stock based compensation expense	431	431	431
Valencia’s transactions with its owner	(3,909)					(3,909)	(3,908)					(3,908)
Ending balance at Jun. 30, 2018	1,788,315	1,722,715	1,149,646	(103,757)	676,826	65,600	1,523,612	1,458,012	1,264,918	(106,709)	299,803	65,600
Ending balance TNMP at Jun. 30, 2018													648,748	64	504,166	144,518
Beginning balance at Dec. 31, 2018	1,752,594	1,688,382	1,153,113	(108,684)	643,953	64,212	1,461,571	1,397,359	1,264,918	(110,422)	242,863	64,212
Beginning balance TNMP at Dec. 31, 2018	1,688,382						1,397,359						674,093	64	534,166	139,863
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) before subsidiary preferred stock dividends	(50,622)	(56,950)			(56,950)	6,328	(61,340)	(67,668)			(67,668)	6,328
Net earnings							(67,668)						19,365			19,365
Total other comprehensive income	8,502	8,502		8,502			10,474	10,474		10,474
Subsidiary preferred stock dividends	(264)	(264)			(264)
Dividends declared on preferred stock							(264)	(264)			(264)
Dividends declared on common stock	(23,099)	(23,099)			(23,099)								(14,811)			(14,811)
Proceeds from stock option exercise	943	943	943
Awards of common stock	(9,892)	(9,892)	(9,892)
Stock based compensation expense	4,526	4,526	4,526
Valencia’s transactions with its owner	(7,948)					(7,948)	(7,948)					(7,948)
Ending balance at Jun. 30, 2019	1,674,740	1,612,148	1,148,690	(100,182)	563,640	62,592	1,402,493	1,339,901	1,264,918	(99,948)	174,931	62,592
Ending balance TNMP at Jun. 30, 2019	1,612,148						1,339,901						678,647	64	534,166	144,417
Beginning balance at Mar. 31, 2019	1,747,458	1,684,679	1,148,364	(103,239)	639,554	62,779	1,485,307	1,422,528	1,264,918	(104,265)	261,875	62,779
Beginning balance TNMP at Mar. 31, 2019													667,478	64	534,166	133,248
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) before subsidiary preferred stock dividends	(72,283)	(75,782)			(75,782)	3,499	(83,313)	(86,812)			(86,812)	3,499
Net earnings							(86,812)						15,267			15,267
Total other comprehensive income	3,057	3,057		3,057			4,317	4,317		4,317
Subsidiary preferred stock dividends	(132)	(132)			(132)
Dividends declared on preferred stock							(132)	(132)			(132)
Dividends declared on common stock													(4,098)			(4,098)
Proceeds from stock option exercise	13	13	13
Awards of common stock	(956)	(956)	(956)
Stock based compensation expense	1,269	1,269	1,269
Valencia’s transactions with its owner	(3,686)					(3,686)	(3,686)					(3,686)
Ending balance at Jun. 30, 2019	1,674,740	$ 1,612,148	$ 1,148,690	$ (100,182)	$ 563,640	$ 62,592	1,402,493	$ 1,339,901	$ 1,264,918	$ (99,948)	$ 174,931	$ 62,592
Ending balance TNMP at Jun. 30, 2019	$ 1,612,148						$ 1,339,901						$ 678,647	$ 64	$ 534,166	$ 144,417