Risk Management and Fair Values (Schedules Of Valuation Techniques) (Details) - Parent Company [Member] $ in Millions	Sep. 30, 2015 USD ($)
Range From Average Percentage for Electricity Options	64.00%
Range from Average Percentage for Fair Value of Electricity Swaps	3.00%
Effect of Significant Unobservable Inputs on Fair Value of Electricity Swaps	$ 7
Effect of Significant Unobservable Inputs on Fair Value of Electricity Options	31
Fair Value of Electricity Options	44
Fair Value of Electricity Swaps	$ 119

The effect of significant unobservable inputs on the fair value of electricity options.

No definition available.

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The effect of significant unobservable inputs on the fair value of electricity swaps.

No definition available.

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The fair value of electricity options classified as Level 3 in the fair value hierarchy.

No definition available.

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The fair value of electricity swaps classified as Level 3 in the fair value hierarchy

No definition available.

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The range from the average percentage used when calculating the fair value of electricity options classified as Level 3 in the fair value hierarchy

No definition available.

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The range from the average percentage used when calculating the fair value of electricity swaps classified as Level 3 in the fair value hierarchy

No definition available.

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