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Commitments, Guarantees and Contingencies - Environmental Matters (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2015 USD ($) MW
Boswell Unit 4 [Member] |
Environmental Matters [Line Items] |
Total Project Costs | $ 220
Minimum [Member] | Coal Combustion Residuals [Member] |
Environmental Matters [Line Items] |
Estimated Costs of Compliance | 80
Maximum [Member] | Clean Water Act - Aquatic Organisms [Member] |
Environmental Matters [Line Items] |
Estimated Costs of Compliance | 15
Maximum [Member] | Coal Combustion Residuals [Member] |
Environmental Matters [Line Items] |
Estimated Costs of Compliance | $ 100
NOV Consent Decree [Member] |
Environmental Matters [Line Items] |
Additional Wind Energy Generating Capacity (MW) | MW | 200
NOV Consent Decree [Member] | Minimum [Member] |
Environmental Matters [Line Items] |
Estimated Capital Expenditures | $ 20
NOV Consent Decree [Member] | Maximum [Member] |
Environmental Matters [Line Items] |
Estimated Capital Expenditures | $ 40

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