Fair Value of Derivative and Other Financial Instruments, Sale of Power (Details) - PNMR and PNM [Member] - Palo Verde Nuclear Generating Station Unit 3 [Member]	Dec. 31, 2015 $ / MWh MW
Sale of Power [Line Items]
Number of megawatts not included in retail rates (in megawatts) | MW	134
Percentage of electric power plant output sold or contracted to sell	100.00%
Commodity Contract [Member]
Sale of Power [Line Items]
Derivative, average forward price (in dollars per megawatt hour) | $ / MWh	26