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Commitments and Contingencies - Nuclear Spent Fuel and Waste Disposal (Details) - Public Service Company of New Mexico [Member] - Palo Verde Nuclear Generating Station [Member] - USD ($) |  | 3 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
May 16, 2014 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Department of energy, spent nuclear fuel removal January 2007 - June 2011 [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
PNM's share of third party settlement claim |  |  |  |  |  | $ 5,900,000
Department of energy, spent nuclear fuel removal July 2011 - June 2014 [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
PNM's share of third party settlement claim |  |  | $ 4,300,000 |  |  |
Litigation settlement, portion credited to customers |  |  | $ 3,100,000 |  |  |
Department of energy, spent nuclear fuel removal July 2014 - June 2015 [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
PNM's share of third party settlement claim |  | $ 1,300,000 |  |  |  |
Litigation settlement, portion credited to customers |  | $ 500,000 |  |  |  |
Nuclear spent fuel and waste disposal [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Estimate of possible loss |  |  |  | $ 57,700,000 |  |
DOE adjusted one-mill fee | $ 0 |  |  |  |  |
Nuclear spent fuel and waste disposal [Member] | Other Deferred Credits [Member] |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |
Liability for interim storage costs |  |  |  | $ 12,100,000 | $ 12,200,000 |

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