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Commitments and Contingencies - National Ambient Air Quality Standards (Details) - parts_per_billion | Feb. 25, 2019 | Sep. 30, 2016 | Oct. 01, 2015
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Public Service Company of New Mexico | Maximum | San Juan Generating Station And Four Corners |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Government standard emissions limit (in parts per billion) | 75 | 75 | 70

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