Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues	$ 347,872		$ 549,498		$ 415,586		$ 387,663		$ 380,651	$ 503,653	$ 405,817	$ 383,396	$ 1,700,619	$ 1,673,517	$ 1,647,744
Intersegment revenues													0	0	0
Total revenues													1,700,619	1,673,517	1,647,744
Cost of energy													692,922	700,727	717,989
Gross margin													1,007,697	972,790	929,755
Other operating expenses													593,351	581,634	589,864
Depreciation and amortization													157,047	151,704	147,949
Operating income (Loss)	63,935		108,284		32,860		52,220		49,888	105,408	73,674	10,482	257,299	239,452	191,942
Interest income													15,515	18,896	28,389
Gain on sale of First Choice													174,925	0	0
Equity in net earnings (loss) of Optim Energy														(203,399)
Equity in net earnings (loss) of Optim Energy													0	(15,223)	(30,145)
Other income (deductions)													(10,421)	7,045	26,770
Net interest charges													(124,849)	(125,373)	(122,205)
Earnings (Loss) before Income Taxes													312,469	(63,379)	94,751
Income taxes (benefit)													121,535	(32,255)	28,818
Net earnings (loss) excluding subsidiary preferred stock dividends	115,408	[1]	47,905	[1]	7,669	[1]	19,952	[1]	(104,805)	52,593	26,302	(5,214)	190,934	(31,124)	136,734
Earnings (loss) from continuing operations															65,933
Valencia non-controlling interest													(14,047)	(13,563)	(11,890)
Preferred Stock Dividend Requirements of Subsidiary													(528)	(528)	(528)
Segment earnings (loss) from continuing operations attributable to PNMR (excluding discontinued operations amounts related to sale of PNM Gas)															53,515
Net earnings (loss) attributable to PNMR	111,993		43,662		4,067		16,637		(108,196)	48,552	22,878	(8,449)	176,359	(45,215)	124,316
Gross property additions													326,931	281,488	288,031
Gross property additions															284,597	[2]
Total Assets	5,204,613								5,225,083				5,204,613	5,225,083	5,359,921
Goodwill	278,297								321,310				278,297	321,310	321,310
Additions to utility and non-utility plant included in accounts payable	33,655												33,655
PNM Electric [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues													1,057,289	1,017,128	967,998
Intersegment revenues													0	0	11
Total revenues													1,057,289	1,017,128	968,009
Cost of energy													362,237	352,270	378,145
Gross margin													695,052	664,858	589,864
Other operating expenses													438,822	424,455	420,473
Depreciation and amortization													94,787	92,281	92,140
Operating income (Loss)													161,443	148,122	77,251
Interest income													15,562	18,854	30,543
Gain on sale of First Choice													0
Equity in net earnings (loss) of Optim Energy														0
Equity in net earnings (loss) of Optim Energy															0
Other income (deductions)													4,309	12,712	6,891
Net interest charges													(75,349)	(72,400)	(69,058)
Earnings (Loss) before Income Taxes													105,965	107,288	45,627
Income taxes (benefit)													37,427	36,427	13,726
Net earnings (loss) excluding subsidiary preferred stock dividends													68,538	70,861
Earnings (loss) from continuing operations															31,901
Valencia non-controlling interest													(14,047)	(13,563)	(11,890)
Preferred Stock Dividend Requirements of Subsidiary													(528)	(528)	528
Segment earnings (loss) from continuing operations attributable to PNMR (excluding discontinued operations amounts related to sale of PNM Gas)															19,483
Net earnings (loss) attributable to PNMR													53,963	56,770
Gross property additions													251,345	226,766
Gross property additions															253,335	[2]
Total Assets	4,095,287								3,875,573				4,095,287	3,875,573	3,775,166
Goodwill	51,632								51,632				51,632	51,632	51,632
Additions to utility and non-utility plant included in accounts payable	26,815												26,815
TNMP Electric [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues													204,045	173,504	151,294
Intersegment revenues													33,813	39,084	41,338
Total revenues													237,858	212,588	192,632
Cost of energy													41,166	37,064	34,728
Gross margin													196,692	175,524	157,904
Other operating expenses													88,234	77,387	75,540
Depreciation and amortization													44,616	41,726	37,262
Operating income (Loss)													63,842	56,411	45,102
Interest income													2	1	9
Gain on sale of First Choice													0
Equity in net earnings (loss) of Optim Energy														0
Equity in net earnings (loss) of Optim Energy															0
Other income (deductions)													1,580	771	2,860
Net interest charges													(29,286)	(31,157)	(27,820)
Earnings (Loss) before Income Taxes													36,138	26,026	20,151
Income taxes (benefit)													13,881	10,044	7,985
Valencia non-controlling interest													0	0	0
Preferred Stock Dividend Requirements of Subsidiary													0	0	0
Net earnings (loss) attributable to PNMR													22,257	15,982	12,166
Gross property additions													67,407	41,018
Gross property additions															53,063	[2]
Total Assets	1,037,445								1,010,957				1,037,445	1,010,957	1,009,055
Goodwill	226,665								226,665				226,665	226,665	226,665
Additions to utility and non-utility plant included in accounts payable	4,736												4,736
First Choice [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues													439,450	483,203	528,818
Intersegment revenues													0	0	0
Total revenues													439,450	483,203	528,818
Cost of energy													323,331	350,476	346,454
Gross margin													116,119	132,727	182,364
Other operating expenses													75,966	92,077	107,354
Depreciation and amortization													1,098	864	1,809
Operating income (Loss)													39,055	39,786	73,201
Interest income													64	18	56
Gain on sale of First Choice													0
Equity in net earnings (loss) of Optim Energy														0
Equity in net earnings (loss) of Optim Energy															0
Other income (deductions)													(650)	(411)	(438)
Net interest charges													(581)	(1,268)	(2,782)
Earnings (Loss) before Income Taxes													37,888	38,125	70,037
Income taxes (benefit)													13,772	14,064	25,622
Valencia non-controlling interest													0	0	0
Preferred Stock Dividend Requirements of Subsidiary													0	0	0
Net earnings (loss) attributable to PNMR													24,116	24,061	44,415
Gross property additions													2,089	3,046
Gross property additions															863	[2]
Total Assets	0								218,411				0	218,411	197,062
Goodwill	0								43,013				0	43,013	43,013
Additions to utility and non-utility plant included in accounts payable	0												0
Corporate and Other [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating revenues													(165)	(318)	(366)
Intersegment revenues													(33,813)	(39,084)	(41,349)
Total revenues													(33,978)	(39,402)	(41,715)
Cost of energy													(33,812)	(39,083)	(41,338)
Gross margin													(166)	(319)	(377)
Other operating expenses													(9,671)	(12,285)	(13,503)
Depreciation and amortization													16,546	16,833	16,738
Operating income (Loss)													(7,041)	(4,867)	(3,612)
Interest income													(113)	23	(2,219)
Gain on sale of First Choice													174,925
Equity in net earnings (loss) of Optim Energy														(203,399)
Equity in net earnings (loss) of Optim Energy															(30,145)
Other income (deductions)													(15,660)	(6,027)	17,457
Net interest charges													(19,633)	(20,548)	(22,545)
Earnings (Loss) before Income Taxes													132,478	(234,818)	(41,064)
Income taxes (benefit)													56,455	(92,790)	(18,515)
Valencia non-controlling interest													0	0	0
Preferred Stock Dividend Requirements of Subsidiary													0	0	0
Net earnings (loss) attributable to PNMR													76,023	(142,028)	(22,549)
Gross property additions													6,090	10,658
Gross property additions															16,462	[2]
Total Assets	71,881								120,142				71,881	120,142	378,638
Goodwill	0								0				0	0	0
Additions to utility and non-utility plant included in accounts payable	$ 2,104												$ 2,104

[1] During the fourth quarter of 2011, PNMR completed the sale of First Choice which resulted in a $174.9 million ($97.0 million after-tax) gain, that positively affected net earnings, net earnings attributable to PNMR, and earnings per share. See Note 2.

[2] Excludes gross property additions related to PNM Gas discontinued operations of $3,434 and includes PNM’s purchase of an interest in PVNGS Unit 2 from another subsidiary of PNMR of $39,126.