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Commitments and Contingencies - Nuclear Spent Fuel and Waste Disposal (Details) - PNM - Nuclear spent fuel and waste disposal - Palo Verde Nuclear Generating Station - USD ($) $ in Millions | Sep. 30, 2020 | Dec. 31, 2019
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Public Utilities, Commitments And Contingencies [Line Items] |  |
Estimate of possible loss | $ 59.6 |
Other deferred credits |  |
Public Utilities, Commitments And Contingencies [Line Items] |  |
Loss contingency accrual | $ 13.1 | $ 12.7

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