Available-For-Sale Securities (Fair Value Of Rabbi Trust) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Total Rabbi Trust Available-for-Sale Securities	$ 183	$ 172
Power [Member]
Total Rabbi Trust Available-for-Sale Securities	36	33
PSE And G [Member]
Total Rabbi Trust Available-for-Sale Securities	61	57
Other [Member]
Total Rabbi Trust Available-for-Sale Securities	$ 86	$ 82

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

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+ Details