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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 | 9 Months Ended | 12 Months Ended | 45 Months Ended
--- | --- | --- | ---
Dec. 31, 2012 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2015
Loss on Derivatives [Member] |  |  |  |  |
Commodity contracts: |  |  |  |  |
Electricity | $ 63 | $ 11 | $ 25 | $ 60 | $ 159
Natural gas | 111 | 7 | 30 | 83 | 231
Net unrealized loss | $ 174 | $ 18 | $ 55 | $ 143 | $ 390

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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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