Condensed Consolidated Statement 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 before subsidiary preferred stock dividends	18,799	15,122			15,122	3,677	11,514	7,837			7,837	3,677
Net earnings							7,837						9,413			9,413
Total other comprehensive income	1,628	1,628		1,628			282	282		282
Subsidiary preferred stock dividends	(132)	(132)			(132)
Dividends declared on preferred stock							(132)	(132)			(132)
Dividends declared on common stock	(21,108)	(21,108)			(21,108)								(1,024)			(1,024)
Proceeds from stock option exercise	802	802	802
Awards of common stock	(10,845)	(10,845)	(10,845)
Stock based compensation expense	2,894	2,894	2,894
Valencia’s transactions with its owner	(4,472)					(4,472)	(4,472)					(4,472)
Ending 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
Ending balance TNMP at Mar. 31, 2018													642,794	64	504,166	138,564
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 before subsidiary preferred stock dividends	21,662	18,832			18,832	2,830	21,974	19,144			19,144	2,830
Net earnings							19,144						4,098			4,098
Total other comprehensive income	5,445	5,445		5,445			6,157	6,157		6,157
Subsidiary preferred stock dividends	(132)	(132)			(132)
Dividends declared on preferred stock							(132)	(132)			(132)
Dividends declared on common stock	(23,099)	(23,099)			(23,099)								(10,713)			(10,713)
Proceeds from stock option exercise	930	930	930
Awards of common stock	(8,936)	(8,936)	(8,936)
Stock based compensation expense	3,257	3,257	3,257
Valencia’s transactions with its owner	(4,263)					(4,263)	(4,263)					(4,263)
Ending 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
Ending balance TNMP at Mar. 31, 2019	$ 1,684,679						$ 1,422,528						$ 667,478	$ 64	$ 534,166	$ 133,248