Franchises and Significant Customers Franchises and Significant Customers (Details)	12 Months Ended	1 Months Ended		12 Months Ended
	Dec. 31, 2011	Apr. 30, 1999 White Sands	Mar. 31, 2006 Holloman	Dec. 31, 2011 July 1, 2005 through August 1, 2010 El Paso		Dec. 31, 2011 August 1, 2010 through Present El Paso		Dec. 31, 2011 February 1, 2000 through Present Las Cruces		Dec. 31, 2011 Sales Revenue, Services, Net Military Bases
Franchises and Significant Customers [Line Items]
Percentage of Revenue From Franchise Fees				3.25%	[1]	4.00%	[1],[2]	2.00%	[1]
Percentage of Revenue Additional Franchise Fees, Restricted	0.75%
Concentration Risk, Percentage										5.00%
Contract Term To Provide Retail Electric Service		10 years
Contract Term to Provide Retail Electric Service			10 years

[1] Based on a percentage of revenue.

[2] The additional fee of 0.75% is to be placed in a restricted fund to be used solely for economic development and renewable energy purposes.