Available-For-Sale Securities (Fair Value Of Rabbi Trust) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Total Rabbi Trust Available-for-Sale Securities	$ 175	$ 185
Power [Member]
Total Rabbi Trust Available-for-Sale Securities	38	36
PSE And G [Member]
Total Rabbi Trust Available-for-Sale Securities	41	61
Other Entity [Member]
Total Rabbi Trust Available-for-Sale Securities	$ 96	$ 88

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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+ Details