Related Party Transactions (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Electricity, transmission and distribution related services [Member] | TNMP to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	$ 0	$ 0	$ 33,813
Service billings [Member] | TNMP to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	7	15	164
Service billings [Member] | PNMR to PNM [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	92,597	99,986	98,914
Service billings [Member] | PNMR to TNMP [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	28,937	29,110	29,353
Service billings [Member] | PNM to TNMP [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	562	595	550
Service billings [Member] | PNMR to Optim Energy [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	0	0	4,083
Service billings [Member] | Optim Energy to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	0	0	23
Income tax sharing payments [Member] | TNMP to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	3,643	0	0
Income tax sharing payments [Member] | PNMR to PNM [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	77,433	63,114	0
Income tax sharing payments [Member] | PNMR to TNMP [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	0	1,951	0
Interest charges [Member] | TNMP to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	481	137	40
Interest charges [Member] | PNM to PNMR [Member]
Related Party Transaction [Line Items]
Amount of related party transaction	$ 4	$ 1	$ 54