Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Service billings [Member] | PNMR to PNM [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	$ 90,827	$ 86,871	$ 92,597
Service billings [Member] | PNMR to TNMP [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	28,109	28,349	28,937
Service billings [Member] | PNM to TNMP [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	554	524	562
Service billings [Member] | TNMP to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	41	31	7
Income tax sharing payments [Member] | PNMR to PNM [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	1,450	0	77,433
Income tax sharing payments [Member] | PNMR to TNMP [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	0	0	0
Income tax sharing payments [Member] | TNMP to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	0	0	3,643
Interest charges [Member] | TNMP to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	276	309	481
Interest charges [Member] | PNM to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	$ 54	$ 65	$ 4