Fair Value of Derivative and Other Financial Instruments, Available for Sale Securities (Details) (PNMR and PNM [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	$ 235,894		$ 235,894		$ 226,855
Available-for-sale securities, Unrealized gains			41,272		42,602
Proceeds from sales	29,103	103,230	82,222	179,336
Gross realized gains	3,134	2,719	11,616	8,962
Gross realized (losses)	(2,172)	(531)	(3,382)	(2,027)
Cash and equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	3,338		3,338		3,356
Available-for-sale securities, Unrealized gains			0		0
Domestic value [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	41,917		41,917		39,460
Available-for-sale securities, Unrealized gains			15,360		14,523
Domestic growth [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	74,647		74,647		76,292
Available-for-sale securities, Unrealized gains			18,452		25,656
International and other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	16,957		16,957		16,633
Available-for-sale securities, Unrealized gains			1,339		1,040
U.S. Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	19,616		19,616		21,941
Available-for-sale securities, Unrealized gains			520		158
Municipals [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	67,595		67,595		58,568
Available-for-sale securities, Unrealized gains			4,970		1,018
Corporate and other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	11,824		11,824		10,605
Available-for-sale securities, Unrealized gains			631		207
Fair Value, Measurements, Recurring [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	235,894		235,894		226,855
Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	231,400		231,400		222,500
Fair Value, Measurements, Recurring [Member] | Mine Reclamation Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	4,500		4,500		4,400
Fair Value, Measurements, Recurring [Member] | Cash and equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	3,338		3,338		3,356
Fair Value, Measurements, Recurring [Member] | Domestic value [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	41,917		41,917		39,460
Fair Value, Measurements, Recurring [Member] | Domestic growth [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	74,647		74,647		76,292
Fair Value, Measurements, Recurring [Member] | International and other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	16,957		16,957		16,633
Fair Value, Measurements, Recurring [Member] | U.S. Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	19,616		19,616		21,941
Fair Value, Measurements, Recurring [Member] | Municipals [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	67,595		67,595		58,568
Fair Value, Measurements, Recurring [Member] | Corporate and other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Fair value	$ 11,824		$ 11,824		$ 10,605