Segment Information - Schedule (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Electric Operating Revenues	$ 336,225	$ 400,374	$ 315,391	$ 310,961	$ 335,894	$ 417,433	$ 352,887	$ 332,868	$ 1,362,951	$ 1,439,082	$ 1,435,853
Cost of energy									380,596	464,649	471,556
Utility margin									982,355	974,433	964,297
Other operating expenses									495,260	664,164	491,966
Depreciation and amortization									209,110	185,919	172,634
Operating income	63,584	108,071	64,822	41,508	(119,138)	121,505	72,414	49,569	277,985	124,350	299,697
Interest income									22,293	6,498	8,483
Other income (deductions)									23,529	30,165	12,094
Interest charges									(128,633)	(114,860)	(119,627)
Earnings before Income Taxes									195,174	46,153	200,647
Income taxes (benefit)									63,278	15,075	69,738
Net Earnings	28,423	$ 58,556	$ 30,952	$ 13,965	(87,284)	$ 64,855	$ 35,655	$ 17,852	131,896	31,078	130,909
Valencia non-controlling interest									(14,519)	(14,910)	(14,127)
Subsidiary preferred stock dividends									(528)	(528)	(528)
Segment earnings (loss) attributable to PNMR									116,849	15,640	116,254
Total Assets	6,471,080				6,009,328				6,471,080	6,009,328	5,790,237
Goodwill	278,297				278,297				278,297	278,297	278,297
PNM [Member]
Segment Reporting Information [Line Items]
Electric Operating Revenues									1,035,913	1,131,195	1,147,914
Cost of energy									299,714	391,131	403,626
Utility margin									736,199	740,064	744,288
Other operating expenses									414,662	590,967	422,051
Depreciation and amortization									133,447	115,717	109,524
Operating income									188,090	33,380	212,713
Interest income									10,173	6,574	8,557
Other income (deductions)									22,066	26,914	12,258
Interest charges									(87,469)	(79,950)	(79,442)
Earnings before Income Taxes									132,860	(13,082)	154,086
Income taxes (benefit)									40,922	(12,758)	52,633
Net Earnings									91,938	(324)	101,453
Valencia non-controlling interest									(14,519)	(14,910)	(14,127)
Subsidiary preferred stock dividends									(528)	(528)	(528)
Segment earnings (loss) attributable to PNMR									76,891	(15,762)	86,798
Total Assets	4,867,546				4,599,344				4,867,546	4,599,344	4,453,114
Goodwill	51,632				51,632				51,632	51,632	51,632
TNMP [Member]
Segment Reporting Information [Line Items]
Electric Operating Revenues									327,038	307,887	287,939
Cost of energy									80,882	73,518	67,930
Utility margin									246,156	234,369	220,009
Other operating expenses									93,389	88,051	84,365
Depreciation and amortization									61,126	56,285	50,056
Operating income									91,641	90,033	85,588
Interest income									0	0	0
Other income (deductions)									3,202	3,736	2,138
Interest charges									(29,335)	(27,681)	(27,396)
Earnings before Income Taxes									65,508	66,088	60,330
Income taxes (benefit)									23,836	24,125	22,523
Net Earnings									41,672	41,963	37,807
Valencia non-controlling interest									0	0	0
Subsidiary preferred stock dividends									0	0	0
Segment earnings (loss) attributable to PNMR									41,672	41,963	37,807
Total Assets	1,383,223				1,297,139				1,383,223	1,297,139	1,229,417
Goodwill	226,665				226,665				226,665	226,665	226,665
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Electric Operating Revenues									0	0	0
Cost of energy									0	0	0
Utility margin									0	0	0
Other operating expenses									(12,791)	(14,854)	(14,450)
Depreciation and amortization									14,537	13,917	13,054
Operating income									(1,746)	937	1,396
Interest income									12,120	(76)	(74)
Other income (deductions)									(1,739)	(485)	(2,302)
Interest charges									(11,829)	(7,229)	(12,789)
Earnings before Income Taxes									(3,194)	(6,853)	(13,769)
Income taxes (benefit)									(1,480)	3,708	(5,418)
Net Earnings									(1,714)	(10,561)	(8,351)
Valencia non-controlling interest									0	0	0
Subsidiary preferred stock dividends									0	0	0
Segment earnings (loss) attributable to PNMR									(1,714)	(10,561)	(8,351)
Total Assets	220,311				112,845				220,311	112,845	107,706
Goodwill	$ 0				$ 0				$ 0	$ 0	$ 0