Asset Retirement Obligations (Details) (USD $)	12 Months Ended																			12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009		Dec. 31, 2011 Public Service Company of New Mexico [Member]		Dec. 31, 2010 Public Service Company of New Mexico [Member]		Dec. 31, 2009 Public Service Company of New Mexico [Member]		Dec. 31, 2011 Texas-New Mexico Power Company [Member]		Dec. 31, 2010 Texas-New Mexico Power Company [Member]		Dec. 31, 2009 Texas-New Mexico Power Company [Member]		Dec. 31, 2008 PNM Gas [Member]	Dec. 31, 2011 Palo Verde Nuclear Generating Station [Member] Public Service Company of New Mexico [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Liability Beginning Balance	$ 76,637,000		$ 70,963,000		$ 63,675,000	[1]	$ 75,888,000		$ 70,099,000		$ 62,879,000	[1]	$ 648,000		$ 771,000		$ 711,000	[1]	$ 200,000
Liabilities incurred	60,000		532,000		3,464,000		60,000		531,000		3,464,000		0		0		0
Liabilities settled	(4,000)		(603,000)		(8,000)		0		(413,000)		(8,000)		(4,000)		(190,000)		0
Accretion expense	6,114,000		6,019,000		5,751,000		6,051,000		5,945,000		5,683,000		55,000		67,000		60,000
Revisions to estimated cash flows	(3,574,000)	[2]	(274,000)	[2]	(1,919,000)	[2]	(3,574,000)	[2]	(274,000)	[2]	(1,919,000)	[2]	0	[2]	0	[2]	0	[2]
Liability Ending Balance	79,233,000		76,637,000		70,963,000		78,425,000		75,888,000		70,099,000		699,000		648,000		771,000		200,000
Asset Retirement Obligation	79,233,000		76,637,000		70,963,000		78,425,000		75,888,000		70,099,000		699,000		648,000		771,000		200,000
Nuclear Decommissioning License Extension Term																				20 years
Asset Retirement Obligation, Period Increase (Decrease)																				$ 4,200,000

[1] ARO for PNMR and PNM includes $0.2 million at December 31, 2008 for PNM Gas.

[2] Based on studies to estimate amount and timing of future ARO expenditures. PNM has an ARO for PVNGS that includes the obligations for nuclear decommissioning of that facility. In 2011, a new decommissioning study for PVNGS reflects updated cash flow estimates and the 20-year license extension, which extends the commencement of decommissioning to 2045. The new study resulted in a $4.2 million decrease to the ARO.