Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Service billings [Member] | PNMR to PNM [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	$ 94,606	$ 90,827	$ 86,871
Service billings [Member] | PNMR to TNMP [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	28,907	28,109	28,349
Service billings [Member] | PNM to TNMP [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	427	554	524
Service billings [Member] | TNMP to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	66	41	31
Income tax sharing payments [Member] | PNMR to PNM [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	0	1,450	0
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	0
Interest payments [Member] | PNMR to PNM [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	150	110	102
Interest payments [Member] | TNMP to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	132	276	309
Interest payments [Member] | PNM to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	$ 11	$ 54	$ 65