Summary of Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2011

Accounting Policies [Abstract]

Schedule of Inventory, Current [Table Text Block]

Inventories consisted of the following at December 31:

	PNMR				PNM				TNMP
	2011		2010		2011		2010		2011		2010
	(In thousands)
Coal	$	17,175	$	17,115	$	17,175	$	17,115	$	—	$	—
Materials and supplies	37,056		35,364		34,346		32,339		2,710		2,787
	$	54,231	$	52,479	$	51,521	$	49,454	$	2,710	$	2,787

Schedule of Average Rates Used Allocated Between Depreciation Expense and Construction Expense Projects Based on Use of Equipment [Table Text Block]

Average rates used are as follows:

	Year ended December 31
	2011		2010		2009
PNM
Electric plant	2.24	%	2.24	%	2.31	%
Common, intangible, and general plant	6.03	%	5.63	%	4.29	%
TNMP	3.41	%	3.39	%	3.44	%