Condensed Consolidated Statements of Changes in Equity - USD ($)	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, 2018	$ 1,752,594,000	$ 1,688,382,000	$ 1,153,113,000	$ (108,684,000)	$ 643,953,000	$ 64,212,000	$ 1,461,571,000	$ 1,397,359,000	$ 1,264,918,000	$ (110,422,000)	$ 242,863,000	$ 64,212,000
Beginning balance TNMP at Dec. 31, 2018													$ 674,093,000	$ 64,000	$ 534,166,000	$ 139,863,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings before subsidiary preferred stock dividends	56,141,000	45,953,000			45,953,000	10,188,000	23,381,000	13,193,000			13,193,000	10,188,000
Net earnings							13,193,000						44,452,000			44,452,000
Total other comprehensive income	9,803,000	9,803,000		9,803,000			12,008,000	12,008,000		12,008,000
Subsidiary preferred stock dividends	(396,000)	(396,000)			(396,000)
Dividends declared on preferred stock							(396,000)	(396,000)			(396,000)
Dividends declared on common stock	(69,299,000)	(69,299,000)			(69,299,000)		0						(30,178,000)			(30,178,000)
Proceeds from stock option exercise	943,000	943,000	943,000
Awards of common stock	(9,897,000)	(9,897,000)	(9,897,000)
Stock based compensation expense	5,424,000	5,424,000	5,424,000
Valencia’s transactions with its owner	(10,225,000)					(10,225,000)	(10,225,000)					(10,225,000)
Ending balance at Sep. 30, 2019	1,735,088,000	1,670,913,000	1,149,583,000	(98,881,000)	620,211,000	64,175,000	1,486,339,000	1,422,164,000	1,264,918,000	(98,414,000)	255,660,000	64,175,000
Ending balance TNMP at Sep. 30, 2019													688,367,000	64,000	534,166,000	154,137,000
Beginning balance at Jun. 30, 2019	1,674,740,000	1,612,148,000	1,148,690,000	(100,182,000)	563,640,000	62,592,000	1,402,493,000	1,339,901,000	1,264,918,000	(99,948,000)	174,931,000	62,592,000
Beginning balance TNMP at Jun. 30, 2019													678,647,000	64,000	534,166,000	144,417,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings before subsidiary preferred stock dividends	106,763,000	102,903,000			102,903,000	3,860,000	84,721,000	80,861,000			80,861,000	3,860,000
Net earnings							80,861,000						25,087,000			25,087,000
Total other comprehensive income	1,301,000	1,301,000		1,301,000			1,534,000	1,534,000		1,534,000
Subsidiary preferred stock dividends	(132,000)	(132,000)			(132,000)
Dividends declared on preferred stock							(132,000)	(132,000)			(132,000)
Dividends declared on common stock	(46,200,000)	(46,200,000)			(46,200,000)		0						(15,367,000)			(15,367,000)
Awards of common stock	(5,000)	(5,000)	(5,000)
Stock based compensation expense	898,000	898,000	898,000
Valencia’s transactions with its owner	(2,277,000)					(2,277,000)	(2,277,000)					(2,277,000)
Ending balance at Sep. 30, 2019	1,735,088,000	1,670,913,000	1,149,583,000	(98,881,000)	620,211,000	64,175,000	1,486,339,000	1,422,164,000	1,264,918,000	(98,414,000)	255,660,000	64,175,000
Ending balance TNMP at Sep. 30, 2019													688,367,000	64,000	534,166,000	154,137,000
Beginning balance at Dec. 31, 2019	1,741,750,000	1,678,698,000	1,150,552,000	(99,377,000)	627,523,000	63,052,000	1,512,431,000	1,449,379,000	1,264,918,000	(99,055,000)	283,516,000	63,052,000
Beginning balance TNMP at Dec. 31, 2019	1,678,698,000						1,449,379,000						754,627,000	64,000	614,166,000	140,397,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings before subsidiary preferred stock dividends	175,615,000	164,393,000			164,393,000	11,222,000	140,420,000	129,198,000			129,198,000	11,222,000
Net earnings							129,198,000						47,187,000			47,187,000
Total other comprehensive income	9,501,000	9,501,000		9,501,000			10,310,000	10,310,000		10,310,000
Subsidiary preferred stock dividends	(396,000)	(396,000)			(396,000)
Dividends declared on preferred stock							(396,000)	(396,000)			(396,000)
Dividends declared on common stock	(73,480,000)	(73,480,000)			(73,480,000)		(40,654,000)	(40,654,000)			(40,654,000)		(34,613,000)			(34,613,000)
Proceeds from stock option exercise	24,000	24,000	24,000
Awards of common stock	(11,984,000)	(11,984,000)	(11,984,000)
Stock based compensation expense	6,560,000	6,560,000	6,560,000
Valencia’s transactions with its owner	(14,995,000)					(14,995,000)	(14,995,000)					(14,995,000)
Ending balance at Sep. 30, 2020	1,832,595,000	1,773,316,000	1,145,152,000	(89,876,000)	718,040,000	59,279,000	1,607,116,000	1,547,837,000	1,264,918,000	(88,745,000)	371,664,000	59,279,000
Ending balance TNMP at Sep. 30, 2020	1,773,316,000						1,547,837,000						767,201,000	64,000	614,166,000	152,971,000
Beginning balance at Jun. 30, 2020	1,756,427,000	1,696,500,000	1,143,822,000	(92,581,000)	645,259,000	59,927,000	1,506,198,000	1,446,271,000	1,264,918,000	(90,992,000)	272,345,000	59,927,000
Beginning balance TNMP at Jun. 30, 2020													759,454,000	64,000	614,166,000	145,224,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings before subsidiary preferred stock dividends	125,453,000	121,900,000			121,900,000	3,553,000	103,004,000	99,451,000			99,451,000	3,553,000
Net earnings							99,451,000						23,921,000			23,921,000
Total other comprehensive income	2,705,000	2,705,000		2,705,000			2,247,000	2,247,000		2,247,000
Subsidiary preferred stock dividends	(132,000)	(132,000)			(132,000)
Dividends declared on preferred stock							(132,000)	(132,000)			(132,000)
Dividends declared on common stock	(48,987,000)	(48,987,000)			(48,987,000)		0						(16,174,000)			(16,174,000)
Stock based compensation expense	1,330,000	1,330,000	1,330,000
Valencia’s transactions with its owner	(4,201,000)					(4,201,000)	(4,201,000)					(4,201,000)
Ending balance at Sep. 30, 2020	1,832,595,000	$ 1,773,316,000	$ 1,145,152,000	$ (89,876,000)	$ 718,040,000	$ 59,279,000	1,607,116,000	$ 1,547,837,000	$ 1,264,918,000	$ (88,745,000)	$ 371,664,000	$ 59,279,000
Ending balance TNMP at Sep. 30, 2020	$ 1,773,316,000						$ 1,547,837,000						$ 767,201,000	$ 64,000	$ 614,166,000	$ 152,971,000