Segment Information - Narrative (Details) - Electric operating revenues [Member] - customer	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
PNMR and PNM [Member]
Concentration Risk [Line Items]
Number of customers that make up more than 10% of total revenue	0
PNMR and PNM [Member] | Maximum [Member]
Concentration Risk [Line Items]
Operating revenues from continuing operations	10.00%
Texas-New Mexico Power Company [Member]
Concentration Risk [Line Items]
Number of customers that make up more than 10% of total revenue	3
Texas-New Mexico Power Company [Member] | Unaffiliated Customer of Texas-New Mexico Power Company One [Member]
Concentration Risk [Line Items]
Operating revenues from continuing operations	16.00%	15.00%	16.00%
Texas-New Mexico Power Company [Member] | Unaffiliated Customer of Texas-New Mexico Power Company Three [Member]
Concentration Risk [Line Items]
Operating revenues from continuing operations	13.00%	15.00%	17.00%
Texas-New Mexico Power Company [Member] | Unaffiliated Customer of Texas-New Mexico Power Company Two [Member]
Concentration Risk [Line Items]
Operating revenues from continuing operations	11.00%	11.00%	10.00%