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Commitments and Contingencies - Clean Air Act, Lawsuits (Details) - USD ($) $ in Millions |  | 1 Months Ended
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Aug. 17, 2015 | May 31, 2010
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Mercury Control [Member] |  |
Loss Contingencies [Line Items] |  |
Current annual mercury control costs |  | $ 0.7
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Mercury Control [Member] | Maximum [Member] |  |
Loss Contingencies [Line Items] |  |
Contingent estimated annual mercury control cost |  | $ 6.6
Public Service Company of New Mexico [Member] | Four Corners Units 4 and 5 (Coal) [Member] | Clean Air Act Lawsuit [Member] |  |
Loss Contingencies [Line Items] |  |
Litigation settlement, amount | $ 1.5 |
Litigation settlement, expected capital spend, environmental | $ 6.7 |
Ownership percentage | 13.00% |
Former Four Corners Co-Owner [Member] | Four Corners Units 4 and 5 (Coal) [Member] | Clean Air Act Lawsuit [Member] |  |
Loss Contingencies [Line Items] |  |
Litigation settlement, expected capital spend, environmental | $ 3.2 |
Current Four Corners Co-Owners [Member] | Four Corners Units 4 and 5 (Coal) [Member] | Clean Air Act Lawsuit [Member] |  |
Loss Contingencies [Line Items] |  |
Litigation settlement, expected capital spend, environmental | $ 3.5 |

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- Details
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