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Price Risk Management Future Year Net Unrealized Gain/Loss Recorded at Balance Sheet Date Expected to Become Realized (Details) (Loss on Derivatives [Member], USD $) In Millions, unless otherwise specified | 6 Months Ended | 12 Months Ended | 42 Months Ended
--- | --- | --- | ---
Dec. 31, 2013 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2016
Loss on Derivatives [Member] |  |  |  |  |
Commodity contracts: |  |  |  |  |
Electricity | $ 12 | $ 6 | $ 24 | $ 43 | $ 85
Natural gas | 43 | 6 | 9 | 35 | 93
Net unrealized loss | $ 55 | $ 12 | $ 33 | $ 78 | $ 178

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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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