Fair Value of Derivative and Other Financial Instruments, Recurring (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Disclosure Derivative Reconciling Amount from Contract Value to Fair Value			$ 100,000
Fair Value, Level 1 to level 2 Transfers, Amount	0
Fair Value, Level 2 to level 1 Transfers, Amount	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset and Liability Transfers Into Level 3	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset and Liability, Transfers out of Level 3	0
PNMR and PNM [Member] | Measured on a recurring basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	168,851,000	[1]	156,922,000	[1]
PNMR and PNM [Member] | Measured on a recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	114,259,000		105,997,000
PNMR and PNM [Member] | Measured on a recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	54,592,000		50,925,000
PNMR and PNM [Member] | Measured on a recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Cash and equivalents [Member] | Measured on a recurring basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	2,766,000	[1]	4,986,000	[1]
PNMR and PNM [Member] | Cash and equivalents [Member] | Measured on a recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	2,766,000		4,986,000
PNMR and PNM [Member] | Cash and equivalents [Member] | Measured on a recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Cash and equivalents [Member] | Measured on a recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Domestic value [Member] | Measured on a recurring basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	25,143,000	[1]	25,491,000	[1]
PNMR and PNM [Member] | Domestic value [Member] | Measured on a recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	25,143,000		25,491,000
PNMR and PNM [Member] | Domestic value [Member] | Measured on a recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Domestic value [Member] | Measured on a recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Domestic growth [Member] | Measured on a recurring basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	52,187,000	[1]	48,237,000	[1]
PNMR and PNM [Member] | Domestic growth [Member] | Measured on a recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	52,187,000		48,237,000
PNMR and PNM [Member] | Domestic growth [Member] | Measured on a recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Domestic growth [Member] | Measured on a recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Multinational [Member] | Measured on a recurring basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	12,754,000	[1]	10,670,000	[1]
PNMR and PNM [Member] | Multinational [Member] | Measured on a recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	12,754,000		10,670,000
PNMR and PNM [Member] | Multinational [Member] | Measured on a recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Multinational [Member] | Measured on a recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | U.S. Government [Member] | Measured on a recurring basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	25,367,000	[1]	21,541,000	[1]
PNMR and PNM [Member] | U.S. Government [Member] | Measured on a recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	21,409,000		16,613,000
PNMR and PNM [Member] | U.S. Government [Member] | Measured on a recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	3,958,000		4,928,000
PNMR and PNM [Member] | U.S. Government [Member] | Measured on a recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Municipals [Member] | Measured on a recurring basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	41,463,000	[1]	37,595,000	[1]
PNMR and PNM [Member] | Municipals [Member] | Measured on a recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Municipals [Member] | Measured on a recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	41,463,000		37,595,000
PNMR and PNM [Member] | Municipals [Member] | Measured on a recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Corporate and other [Member] | Measured on a recurring basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	9,171,000	[1]	8,402,000	[1]
PNMR and PNM [Member] | Corporate and other [Member] | Measured on a recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
PNMR and PNM [Member] | Corporate and other [Member] | Measured on a recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	9,171,000		8,402,000
PNMR and PNM [Member] | Corporate and other [Member] | Measured on a recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
NDT Investments	0		0
Public Service Company of New Mexico [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Disclosure Derivative Reconciling Amount from Contract Value to Fair Value	0		0
Commodity Contract [Member] | Measured on a recurring basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets			21,263,000
Commodity derivative instruments, Liabilities			(44,238,000)
Commodity derivative instruments, Net			(22,975,000)	[1]
Commodity Contract [Member] | Measured on a recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets			8,646,000
Commodity derivative instruments, Liabilities			(26,378,000)
Commodity derivative instruments, Net			(17,732,000)
Commodity Contract [Member] | Measured on a recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets			12,308,000
Commodity derivative instruments, Liabilities			(16,729,000)
Commodity derivative instruments, Net			(4,421,000)
Commodity Contract [Member] | Measured on a recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets			272,000
Commodity derivative instruments, Liabilities			(1,094,000)
Commodity derivative instruments, Net			(822,000)
Commodity Contract [Member] | PNMR and PNM [Member] | Measured on a recurring basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets	3,713,000	[1]
Commodity derivative instruments, Liabilities	(4,069,000)	[1]
Commodity derivative instruments, Net	(356,000)	[1]
Commodity Contract [Member] | PNMR and PNM [Member] | Measured on a recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets	0
Commodity derivative instruments, Liabilities	0
Commodity derivative instruments, Net	0
Commodity Contract [Member] | PNMR and PNM [Member] | Measured on a recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets	3,713,000
Commodity derivative instruments, Liabilities	(4,069,000)
Commodity derivative instruments, Net	(356,000)
Commodity Contract [Member] | PNMR and PNM [Member] | Measured on a recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets	0
Commodity derivative instruments, Liabilities	0
Commodity derivative instruments, Net	0
Commodity Contract [Member] | Public Service Company of New Mexico [Member] | Measured on a recurring basis [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets			1,443,000	[1]
Commodity derivative instruments, Liabilities			(5,119,000)	[1]
Commodity derivative instruments, Net			(3,676,000)	[1]
Commodity Contract [Member] | Public Service Company of New Mexico [Member] | Measured on a recurring basis [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets			0
Commodity derivative instruments, Liabilities			0
Commodity derivative instruments, Net			0
Commodity Contract [Member] | Public Service Company of New Mexico [Member] | Measured on a recurring basis [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets			1,443,000
Commodity derivative instruments, Liabilities			(5,119,000)
Commodity derivative instruments, Net			(3,676,000)
Commodity Contract [Member] | Public Service Company of New Mexico [Member] | Measured on a recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative instruments, Assets			0
Commodity derivative instruments, Liabilities			0
Commodity derivative instruments, Net			$ 0

[1] The Level 1, 2 and 3 columns in the above table are presented based on the nature of each instrument. The total column is presented based on the balance sheet classification of the instruments and reflect unit of account reclassifications between commodity derivative assets and commodity derivative liabilities of zero for PNMR and PNM at December 31, 2011 and less than $0.1 million for PNMR and zero for PNM at December 31, 2010. There were no transfers between levels for the twelve months ended December 31, 2011.