Derivative Instruments And Hedging Activities (Cash Flow Hedges Included In Accumulated Other Comprehensive Loss) (Details) (USD $) In Millions	6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010
Accumulated Other Comprehensive Loss After-tax	$ 60	[1]	$ 114	[2]
Portion Expected to be Reclassified to Income during the Next 12 Months	36		58
Minimum pension liability included in AOCL	20		15
Interest Rate [Member]
Accumulated Other Comprehensive Loss After-tax	11	[1]	20	[2]
Portion Expected to be Reclassified to Income during the Next 12 Months	1		3
Maximum Term	254 months		266 months
Energy Commodity [Member]
Accumulated Other Comprehensive Loss After-tax	49	[1],[3]	94	[2],[4]
Portion Expected to be Reclassified to Income during the Next 12 Months	35	[3]	55	[4]
Maximum Term	35 months	[3]	47 months	[4]
Pepco Energy Services [Member]
Accumulated Other Comprehensive Loss After-tax	41
Conectiv Energy [Member]
Minimum pension liability included in AOCL			$ 32

[1] AOCL on PHI's Consolidated Balance Sheet as of June 30, 2011, includes a $20 million balance related to minimum pension liability. This balance is not included in this table as the minimum pension liability is not a cash flow hedge.

[2] AOCL on PHI's Consolidated Balance Sheet as of June 30, 2010, includes a $15 million balance related to minimum pension liability and a $32 million balance related to Conectiv Energy. These balances are not included in this table as the minimum pension liability is not a cash flow hedge and Conectiv Energy is reported as a discontinued operation.

[3] The unrealized derivative losses recorded in AOCL are largely offset by forecasted natural gas and electricity physical purchases for delivery to retail customers that are in gain positions and subject to accrual accounting. These forward purchase contracts are exempted from mark-to-market accounting because they either qualify as normal purchases under FASB guidance on derivatives and hedging or they are not derivative contracts. Under accrual accounting, no asset is recorded on the balance sheet for these contracts, and the purchase cost is not recognized until the period of distribution. Although Pepco Energy Services no longer designates its natural gas derivatives as cash flow hedges effective January 1, 2011, gains or losses previously deferred in AOCL as of December 31, 2010 would remain in AOCL unless it is probable that the hedged forecasted transaction will not occur. At June 30, 2011, the amount remaining in AOCL associated with natural gas derivatives was $41 million.

[4] The unrealized derivative losses recorded in AOCL are largely offset by forecasted natural gas and electricity physical purchases for delivery to retail customers that are in gain positions and subject to accrual accounting. These forward purchase contracts are exempted from mark-to-market accounting because they either qualify as normal purchases under FASB guidance on derivatives and hedging or they are not derivative contracts. Under accrual accounting, no asset is recorded on the balance sheet for these contracts, and the purchase cost is not recognized until the period of distribution.