Fair Value of Derivative and Other Financial Instruments, Statement of Earnings Information (Details) (Commodity Contract [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Economic hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	$ 3,481	$ (48,773)
Cash flow hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	(422)	27,667
Recognized in OCI	422	(18,739)
Electric operating revenues [Member] | Economic hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	5,682	(4,030)
Electric operating revenues [Member] | Cash flow hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	0	29,930
Cost of energy [Member] | Economic hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	(2,201)	(44,743)
Cost of energy [Member] | Cash flow hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	(422)	(2,263)
Public Service Company of New Mexico [Member] | Economic hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	4,624	(9,416)
Public Service Company of New Mexico [Member] | Cash flow hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	0	29,912
Recognized in OCI	0	(20,984)
Public Service Company of New Mexico [Member] | Electric operating revenues [Member] | Economic hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	5,682	(4,030)
Public Service Company of New Mexico [Member] | Electric operating revenues [Member] | Cash flow hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	0	29,930
Public Service Company of New Mexico [Member] | Cost of energy [Member] | Economic hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	(1,058)	(5,386)
Public Service Company of New Mexico [Member] | Cost of energy [Member] | Cash flow hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss)	$ 0	$ (18)