Consolidated Statement Of Cash Flow (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Potomac Electric Power Co [Member]	Sep. 30, 2011 Potomac Electric Power Co [Member]	Sep. 30, 2012 Delmarva Power & Light Co/De [Member]	Sep. 30, 2011 Delmarva Power & Light Co/De [Member]	Sep. 30, 2012 Atlantic City Electric Co [Member]	Sep. 30, 2011 Atlantic City Electric Co [Member]
OPERATING ACTIVITIES
Net income	$ 242	$ 238	$ 101	$ 88	$ 56	$ 56	$ 36	$ 41
Income from discontinued operations	0	(1)
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	343	325	143	128	78	66	92	107
Non-cash rents from cross-border energy lease investments	(39)	(35)
Gain on early termination of finance leases held in trust	(39)	(39)
Deferred income taxes	279	165	170	58	44	81	72	39
Net unrealized (gains) losses on derivatives	(20)	11
Impairment losses	5
Other	(11)	(9)
Changes in:
Accounts receivable	(26)	86	(31)	5	(6)	39	(47)	(12)
Inventories	(36)	(20)	(21)	(10)	(11)	(6)	(5)	(7)
Prepaid expenses	(30)	(14)	5	6			(12)	(25)
Regulatory assets and liabilities, net	(104)	(108)	(67)	(16)	(16)	(34)	(20)	(58)
Accounts payable and accrued liabilities	2	(106)	29	(21)	2	(31)	26	(2)
Pension contributions	(200)	(110)	(85)	(40)	(85)	(40)	(30)	(30)
Pension benefit obligation, excluding contributions	49	39	16	18
Cash collateral related to derivative activities	76	5
Income tax-related prepayments, receivables and payables	(133)	(14)	(86)	92	11	(23)	(51)	49
Interest accrued	38	34	22	19
Other assets and liabilities	23	40	(6)	3	15	22	13	20
Conectiv Energy net assets held for sale		44
Net Cash (Used By) From Operating Activities	419	531	190	330	88	130	74	122
INVESTING ACTIVITIES
Investment in property, plant and equipment	(888)	(639)	(449)	(361)	(219)	(146)	(186)	(96)
Department of Energy capital reimbursement awards received	25	27	23	24			2	3
Proceeds from early termination of finance leases held in trust	202	161
Changes in restricted cash equivalents	(2)	(10)
Net other investing activities	1	(10)	(1)	(8)	(4)		(3)	(11)
Net Cash (Used By) From Investing Activities	(662)	(471)	(427)	(345)	(223)	(146)	(187)	(104)
FINANCING ACTIVITIES
Dividends paid on common stock	(185)	(183)	(35)			(50)	(35)
Common stock issued for the Dividend Reinvestment Plan and employee-related compensation	40	36
Capital contribution from Parent			50		60			60
Redemption of preferred stock		(6)						(6)
Issuances of long-term debt	450	235	200		250	35		200
Reacquisitions of long-term debt	(165)	(60)	(38)		(97)	(35)	(30)	(25)
Issuances of short-term debt, net	116	11	60		(47)		93	(158)
Cost of issuances	(8)	(10)	(4)		(3)
Net other financing activities		(1)	(3)	(3)	8	9	1	(2)
Net Cash (Used By) From Financing Activities	248	22	230	(3)	171	(41)	29	69
Net Decrease in Cash and Cash Equivalents	5	82	(7)	(18)	36	(57)	(84)	87
Cash and Cash Equivalents at Beginning of Period	109	21	12	88	5	69	91	4
CASH AND CASH EQUIVALENTS AT END OF PERIOD	114	103	5	70	41	12	7	91
SUPPLEMENTAL CASH FLOW INFORMATION
Cash (received) paid for income taxes	(2)		(40)	(108)	(24)	(24)	4	(51)
Non-cash activities:
Reclassification of property, plant and equipment to regulatory assets	90		53		37
Reclassification of asset removal costs regulatory liability to accumulated depreciation	$ 61		$ 19		$ 42