Segment Information (Narrative and Major Customers) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2009 Discontinued Operations [Member] Public Service Company of New Mexico [Member]	Dec. 31, 2009 Palo Verde Nuclear Generating Station [Member] Public Service Company of New Mexico [Member]	Dec. 31, 2011 Sales [Member] First Choice [Member]	Dec. 31, 2010 Sales [Member] First Choice [Member]	Dec. 31, 2009 Sales [Member] First Choice [Member]	Dec. 31, 2011 Sales [Member] Unaffiliated Customer of Texas-New Mexico Power Company One [Member]	Dec. 31, 2010 Sales [Member] Unaffiliated Customer of Texas-New Mexico Power Company One [Member]	Dec. 31, 2009 Sales [Member] Unaffiliated Customer of Texas-New Mexico Power Company One [Member]	Dec. 31, 2011 Sales [Member] Unaffiliated Customer of Texas-New Mexico Power Company Two [Member]	Dec. 31, 2010 Sales [Member] Unaffiliated Customer of Texas-New Mexico Power Company Two [Member]	Dec. 31, 2009 Sales [Member] Unaffiliated Customer of Texas-New Mexico Power Company Two [Member]	Dec. 31, 2011 Maximum [Member] Sales [Member] PNMR and PNM [Member]
Concentration Risk [Line Items]
Property Additions, Gross from discontinued operations	$ 3,434
Payments to acquire interest in lease assets		$ 39,126
Operating revenues from continuing operations (as a percent)			17.00%	18.00%	21.00%	19.00%	19.00%	20.00%	12.00%	13.00%	13.00%	10.00%