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Price Risk Management Future year net unrealized gain/loss recorded at balance sheet date expected to become realized (Details) (Gain (Loss) on Derivatives [Member], USD $) In Millions, unless otherwise specified | 12 Months Ended | 36 Months Ended
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2015
Gain (Loss) on Derivatives [Member] |  |  |  |
Commodity contracts: |  |  |  |
Commodity Contracts, Electricity | $ 10 | $ 28 | $ 43 | $ 81
Commodity Contracts, Natural Gas | 6 | 27 | 80 | 113
Net unrealized loss | $ 16 | $ 55 | $ 123 | $ 194

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- Definition Net unrealized gain or loss related to commodity contracts recorded as of the balance sheet date, expected to be realized in the statement of income in a future period as a result of the settlement of the underlying derivative instrument. + References No definition available. + Details
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- Definition Net unrealized gain or loss recorded as of the balance sheet date related to commodity contracts for electricity, expected to be realized in the statement of income in a future period as a result of the settlement of the underlying derivative instrument. + References No definition available. + Details
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- Definition Net unrealized gain or loss recorded as of the balance sheet date related to commodity contracts for natural gas, expected to be realized in the statement of income in a future period as a result of the settlement of the underlying derivative instrument. + References No definition available. + Details
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- Details
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