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Commitments and Contingencies - Liability and Insurance Matters (Details) - Public Service Company of New Mexico - Palo Verde Nuclear Generating Station | 12 Months Ended
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Dec. 31, 2017 USD ($) generating_unit
Public Utilities, General Disclosures [Line Items] |
Number of units (in generating units) | generating_unit | 3
Nuclear Plant |
Public Utilities, General Disclosures [Line Items] |
Ownership percentage in nuclear reactor | 10.20%
Number of units (in generating units) | generating_unit | 3
Maximum potential assessment per incident | $ 38,900,000
Annual payment limitation related to incident | 5,800,000
Aggregate amount of all risk insurance | 2,750,000,000.00
Sublimit amount for non-nuclear property damage losses | 2,250,000,000.00
Retrospective premium assessment | 5,400,000
Nuclear Plant | Commercial Providers |
Public Utilities, General Disclosures [Line Items] |
Liability insurance coverage | 450,000,000
Nuclear Plant | Industry Wide Retrospective Assessment Program |
Public Utilities, General Disclosures [Line Items] |
Liability insurance coverage | 13,000,000,000.0
Nuclear Plant | Maximum |
Public Utilities, General Disclosures [Line Items] |
Liability insurance coverage | $ 13,400,000,000

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