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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%

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