Fair Value of Derivative and Other Financial Instruments, Derivative Balance Sheet Information (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Derivatives, Fair Value [Line Items]
Commodity derivative instruments, Current assets	$ 2,114,000	$ 3,785,000
Commodity derivative instruments, Deferred charges	0	352,000
Commodity derivative instruments, Current liabilities	(4,132,000)	(1,000,000)
Commodity derivative instruments, Long-term liabilities	(1,785,000)	(1,933,000)
PNMR and PNM [Member]
Derivatives, Fair Value [Line Items]
Margin Deposit Assets	1,900,000	1,900,000
Public Service Company of New Mexico [Member]
Derivatives, Fair Value [Line Items]
Commodity derivative instruments, Current assets	2,114,000	3,785,000
Commodity derivative instruments, Deferred charges	0	352,000
Commodity derivative instruments, Current liabilities	(4,132,000)	(1,000,000)
Commodity derivative instruments, Long-term liabilities	(1,785,000)	(1,933,000)
Commodity Contract [Member] | Fair Value Hedging [Member] | PNMR and PNM [Member]
Derivatives, Fair Value [Line Items]
Commodity derivative instruments, Current assets	2,114,000	3,785,000
Commodity derivative instruments, Deferred charges		352,000	0
Commodity derivative instruments, Assets	2,114,000	4,137,000
Commodity derivative instruments, Current liabilities	(4,132,000)	(1,000,000)
Commodity derivative instruments, Long-term liabilities	(1,785,000)	(1,933,000)
Commodity derivative instruments, Liabilities	(5,917,000)	(2,933,000)
Commodity derivative instruments, Net	(3,803,000)	1,204,000
Commodity Contract [Member] | Fuel and Purchased Power Adjustment Clause [Member] | Fair Value Hedging [Member] | Public Service Company of New Mexico [Member]
Derivatives, Fair Value [Line Items]
Commodity derivative instruments, Current assets and liabilities	$ 100,000