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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment (Note 8)	$ 10,382	$ 10,382	$ 0	$ 0	$ 10,382	$ 0
Balance, as adjusted	1,755,254	1,686,334	1,163,661	(92,451)	615,124	68,920
Beginning balance at Dec. 31, 2016	1,744,872	1,675,952	1,163,661	(92,451)	604,742	68,920	$ 1,466,792	$ 1,397,872	$ 1,264,918	$ (92,428)	$ 225,382	$ 68,920
Beginning balance TNMP at Dec. 31, 2016	1,675,952						1,397,872						$ 593,235	$ 64	$ 454,166	$ 139,005
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Earnings	146,004	134,552			134,552	11,452	115,869	104,417		0	104,417	11,452
Net earnings	134,156						104,417						34,535			34,535
Total other comprehensive income	9,950	9,950		9,950			9,823	9,823		9,823	0
Subsidiary preferred stock dividends	(396)	(396)			(396)
Dividends declared on preferred stock							(396)	(396)		0	(396)
Dividends declared on common stock	(57,948)	(57,948)			(57,948)								(29,663)			(29,663)
Proceeds from stock option exercise	1,739	1,739	1,739
Awards of common stock	(13,816)	(13,816)	(13,816)
Stock based compensation expense	5,322	5,322	5,322
Valencia’s transactions with its owner	(12,963)					(12,963)	(12,963)					(12,963)
Ending balance at Sep. 30, 2017	1,833,146	$ 1,765,737	$ 1,156,906	$ (82,501)	$ 691,332	$ 67,409	1,579,125	$ 1,511,716	$ 1,264,918	$ (82,605)	$ 329,403	$ 67,409
Ending balance TNMP at Sep. 30, 2017	$ 1,765,737						$ 1,511,716						$ 598,107	$ 64	$ 454,166	$ 143,877