The amount of pension and other (such as medical, dental and life insurance) postretirement benefit costs recognized during the period for (1) defined benefit plans (periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss) on assets, prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments) and for (2) defined contribution plans (to the extent that a plan's defined contributions to an individual's account are to be made for periods in which that individual renders services, the net cost for a period is the contribution called for in that period; if a plan calls for contributions for periods after an individual retires or terminates, the estimated cost is accrued during the employee's service period).

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+ Details

Pension And Other Postretirement Benefits (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended			12 Months Ended	3 Months Ended			9 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 Retirement Plan [Member]	Dec. 31, 2010 Retirement Plan [Member]	Mar. 31, 2011 Pepco [Member]	Mar. 31, 2011 ACE [Member]	Mar. 31, 2011 Delmarva Power & Light Co/De [Member]	Sep. 30, 2011 Delmarva Power & Light Co/De [Member]	Sep. 30, 2010 Conectiv Energy [Member]	Sep. 30, 2010 Conectiv Energy [Member]
Pension contributions	$ 110	$ 100	$ 110	$ 100	$ 40	$ 30	$ 40	$ 40
One time charges included in pension and other postretirement costs related to sale of entity									$ 6	$ 6
Asset allocation, percentage in equity investments	53.00%
Asset allocation, percentage in fixed income investments	40.00%
Asset allocation, percentage in other investments	7.00%