Fair Value of Derivative and Other Financial Instruments, Available for Sale Securities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Realized impairment loss	$ 4,300,000	$ 700,000	$ 600,000
PNMR and PNM [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	259,042,000	250,145,000
Unrealized Gains	28,820,000	46,348,000
Proceeds from sales	252,174,000	117,989,000	271,140,000
Gross realized gains	29,663,000	15,162,000	14,308,000
Gross realized (losses)	(9,259,000)	(3,964,000)	$ (4,298,000)
Value of other than temporary impairments	0
PNMR and PNM [Member] | Cash and equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	10,700,000	8,276,000
Unrealized Gains	0	0
PNMR and PNM [Member] | Domestic value [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	44,505,000	45,340,000
Unrealized Gains	11,610,000	17,418,000
PNMR and PNM [Member] | Domestic growth [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	61,078,000	74,053,000
Unrealized Gains	11,163,000	21,354,000
PNMR and PNM [Member] | International and other [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	27,961,000	16,599,000
Unrealized Gains	1,569,000	156,000
PNMR and PNM [Member] | U.S. Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	27,880,000	22,563,000
Unrealized Gains	178,000	903,000
PNMR and PNM [Member] | Municipals [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	58,576,000	68,973,000
Unrealized Gains	3,672,000	5,851,000
PNMR and PNM [Member] | Corporate and other [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	28,342,000	14,341,000
Unrealized Gains	628,000	666,000
PNMR and PNM [Member] | Measured on a recurring basis [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	259,042,000	250,145,000
PNMR and PNM [Member] | Measured on a recurring basis [Member] | Nuclear Decommissioning Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	249,100,000	244,600,000
PNMR and PNM [Member] | Measured on a recurring basis [Member] | Mine Reclamation Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	9,900,000	5,500,000
PNMR and PNM [Member] | Measured on a recurring basis [Member] | Cash and equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	10,700,000	8,276,000
PNMR and PNM [Member] | Measured on a recurring basis [Member] | Domestic value [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	44,505,000	45,340,000
PNMR and PNM [Member] | Measured on a recurring basis [Member] | Domestic growth [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	61,078,000	74,053,000
PNMR and PNM [Member] | Measured on a recurring basis [Member] | International and other [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	27,961,000	16,599,000
PNMR and PNM [Member] | Measured on a recurring basis [Member] | U.S. Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	27,880,000	22,563,000
PNMR and PNM [Member] | Measured on a recurring basis [Member] | Municipals [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	58,576,000	68,973,000
PNMR and PNM [Member] | Measured on a recurring basis [Member] | Corporate and other [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 28,342,000	$ 14,341,000