Sale of FCP	3 Months Ended
Mar. 31, 2012
Discontinued Operations and Disposal Groups [Abstract]
Sale of FCP	Sale of First Choice On September 23, 2011, PNMR entered into an agreement for the sale of First Choice to Direct LP, Inc. for $270.0 million, subject to adjustment to reflect the amounts of certain components of working capital at closing. Closing occurred on November 1, 2011, with PNMR receiving $329.3 million, which includes an estimate of the components of working capital. For accounting purposes, the sale was effective as of the close of business on October 31, 2011. PNMR recognized a pre-tax gain of $174.9 million on the sale. The purchaser has indicated to PNMR that it believes the amount paid at closing for working capital at October 31, 2011 was overstated by $2.4 million. PNMR has responded to the purchaser disputing the purchaser's calculation and indicating that the amount paid at closing for working capital at October 31, 2011 was understated by $5.8 million. PNMR believes its calculation is consistent with the terms of the agreement. PNMR cannot predict the outcome of this matter, but does not believe the ultimate resolution of this matter will have a material impact on its financial condition, results of operation, or cash flows. PNMR Services Company is providing certain services at cost to First Choice for a transitional period of up to nine months following closing. Because PNMR continues to have direct cash flows resulting from transmission and distribution services provided by TNMP to First Choice, First Choice is not reflected as discontinued operations. After October 31, 2011, TNMP's revenues from First Choice are not intercompany and are not eliminated in consolidation by PNMR.

Sale of FCP

3 Months Ended

Mar. 31, 2012

Discontinued Operations and Disposal Groups [Abstract]

Sale of First Choice

On September 23, 2011, PNMR entered into an agreement for the sale of First Choice to Direct LP, Inc. for $270.0 million, subject to adjustment to reflect the amounts of certain components of working capital at closing. Closing occurred on November 1, 2011, with PNMR receiving $329.3 million, which includes an estimate of the components of working capital. For accounting purposes, the sale was effective as of the close of business on October 31, 2011. PNMR recognized a pre-tax gain of $174.9 million on the sale. The purchaser has indicated to PNMR that it believes the amount paid at closing for working capital at October 31, 2011 was overstated by $2.4 million. PNMR has responded to the purchaser disputing the purchaser's calculation and indicating that the amount paid at closing for working capital at October 31, 2011 was understated by $5.8 million. PNMR believes its calculation is consistent with the terms of the agreement. PNMR cannot predict the outcome of this matter, but does not believe the ultimate resolution of this matter will have a material impact on its financial condition, results of operation, or cash flows. PNMR Services Company is providing certain services at cost to First Choice for a transitional period of up to nine months following closing. Because PNMR continues to have direct cash flows resulting from transmission and distribution services provided by TNMP to First Choice, First Choice is not reflected as discontinued operations. After October 31, 2011, TNMP's revenues from First Choice are not intercompany and are not eliminated in consolidation by PNMR.