Segment Information - Schedule (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Electric Operating Revenues	$ 335,894	$ 417,433	$ 352,887	$ 332,868	$ 346,845	$ 413,951	$ 346,160	$ 328,897	$ 1,439,082	$ 1,435,853	$ 1,387,923
Cost of energy									464,649	471,556	432,316
Margin									974,433	964,297	955,607
Other operating expenses									664,164	491,966	501,884
Depreciation and amortization									185,919	172,634	166,881
Operating income	(119,138)	121,505	72,414	49,569	62,849	116,799	71,296	48,753	124,350	299,697	286,842
Interest income									6,498	8,483	10,043
Other income (deductions)									30,165	12,094	(368)
Interest charges									(114,860)	(119,627)	(121,448)
Earnings before Income Taxes									46,153	200,647	175,069
Income Taxes									15,075	69,738	59,513
Net Earnings	(87,284)	$ 64,855	$ 35,655	$ 17,852	22,111	$ 59,486	$ 33,181	$ 16,131	31,078	130,909	115,556
Valencia non-controlling interest									(14,910)	(14,127)	(14,521)
Preferred Stock Dividend Requirements of Subsidiary									(528)	(528)	(528)
Segment earnings (loss) attributable to PNMR									15,640	116,254	100,507
Total Assets	6,009,328				5,790,237				6,009,328	5,790,237	5,426,858
Goodwill	278,297				278,297				278,297	278,297	278,297
PNM [Member]
Segment Reporting Information [Line Items]
Electric Operating Revenues									1,131,195	1,147,914	1,116,312
Cost of energy									391,131	403,626	374,710
Margin									740,064	744,288	741,602
Other operating expenses									590,967	422,051	428,591
Depreciation and amortization									115,717	109,524	103,826
Operating income									33,380	212,713	209,185
Interest income									6,574	8,557	10,182
Other income (deductions)									26,914	12,258	11,288
Interest charges									(79,950)	(79,442)	(79,175)
Earnings before Income Taxes									(13,082)	154,086	151,480
Income Taxes									(12,758)	52,633	48,804
Net Earnings									(324)	101,453	102,676
Valencia non-controlling interest									(14,910)	(14,127)	(14,521)
Preferred Stock Dividend Requirements of Subsidiary									(528)	(528)	(528)
Segment earnings (loss) attributable to PNMR									(15,762)	86,798	87,627
Total Assets	4,599,344				4,453,114				4,599,344	4,453,114	4,174,261
Goodwill	51,632				51,632				51,632	51,632	51,632
TNMP [Member]
Segment Reporting Information [Line Items]
Electric Operating Revenues									307,887	287,939	271,611
Cost of energy									73,518	67,930	57,606
Margin									234,369	220,009	214,005
Other operating expenses									88,051	84,365	91,601
Depreciation and amortization									56,285	50,056	50,219
Operating income									90,033	85,588	72,185
Interest income									0	0	0
Other income (deductions)									3,736	2,138	1,919
Interest charges									(27,681)	(27,396)	(27,393)
Earnings before Income Taxes									66,088	60,330	46,711
Income Taxes									24,125	22,523	17,621
Net Earnings									41,963	37,807	29,090
Valencia non-controlling interest									0	0	0
Preferred Stock Dividend Requirements of Subsidiary									0	0	0
Segment earnings (loss) attributable to PNMR									41,963	37,807	29,090
Total Assets	1,297,139				1,229,417				1,297,139	1,229,417	1,151,327
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
Margin									0	0	0
Other operating expenses									(14,854)	(14,450)	(18,308)
Depreciation and amortization									13,917	13,054	12,836
Operating income									937	1,396	5,472
Interest income									(76)	(74)	(139)
Other income (deductions)									(485)	(2,302)	(13,575)
Interest charges									(7,229)	(12,789)	(14,880)
Earnings before Income Taxes									(6,853)	(13,769)	(23,122)
Income Taxes									3,708	(5,418)	(6,912)
Net Earnings									(10,561)	(8,351)	(16,210)
Valencia non-controlling interest									0	0	0
Preferred Stock Dividend Requirements of Subsidiary									0	0	0
Segment earnings (loss) attributable to PNMR									(10,561)	(8,351)	(16,210)
Total Assets	112,845				107,706				112,845	107,706	101,270
Goodwill	$ 0				$ 0				$ 0	$ 0	$ 0