Schedule I - Condensed Financial Information of Parent Company (Statements of Earnings) (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
Condensed Financial Statements, Captions [Line Items]
Operating Expenses									$ 1,443,320	$ 1,434,065	$ 1,455,802
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
Other Income and Deductions:
Equity in net earnings (loss) of Optim Energy									0	(15,223)	(30,145)
Impairment of equity investment in Optim Energy									0	(188,176)	0
Other income									5,309	14,837	31,629
Other deductions									(24,715)	(12,660)	(9,361)
Net other income (deductions)									180,019	(177,458)	25,014
Earnings (Loss) before Income Taxes									312,469	(63,379)	94,751
Income Tax Expense (Benefit)									121,535	(32,255)	28,818
Earnings (Loss) from Continuing Operations									190,934	(31,124)	65,933
Earnings from Discontinued Operations, net of Income Taxes of $0, $0, and $36,687									0	0	70,801
Net Earnings (Loss)	111,993	43,662	4,067	16,637	(108,196)	48,552	22,878	(8,449)	176,359	(45,215)	124,316
PNMR [Member]
Condensed Financial Statements, Captions [Line Items]
Operating Revenues									0	0	0
Operating Expenses									20,547	6,584	8,156
Operating income (Loss)									(20,547)	(6,584)	(8,156)
Other Income and Deductions:
Equity in earnings (loss) of subsidiaries									205,215	96,804	147,293
Equity in earnings (loss) of subsidiaries											76,492
Equity in net earnings (loss) of Optim Energy									0	(15,223)	(30,145)
Impairment of equity investment in Optim Energy									0	(188,176)	0
Other income									59	948	22,916
Other deductions									(34,124)	(25,772)	(26,850)
Net other income (deductions)									171,150	(131,419)	42,413
Earnings (Loss) before Income Taxes									150,603	(138,003)	34,257
Income Tax Expense (Benefit)									(25,756)	(92,788)	(19,258)
Earnings (Loss) from Continuing Operations									176,359	(45,215)	53,515
Earnings from Discontinued Operations, net of Income Taxes of $0, $0, and $36,687									0	0	70,801
Net Earnings (Loss)									$ 176,359	$ (45,215)	$ 124,316