Quarterly Financial Information - Schedule of Quarterly Financial Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information [Line Items]
Total Operating Revenue	$ 1,091	$ 1,344	$ 1,051	$ 1,180	$ 1,056	$ 1,389	$ 1,057	$ 1,123	$ 4,666	$ 4,625	$ 4,964
Total Operating Expenses	936	1,109	906	1,047	954	1,188	932	1,010	3,998	4,084	4,411
Operating Income	155	235	145	133	102	201	125	113	668	541	553
Other Expenses	(58)	(60)	(62)	(59)	(57)	(57)	(52)	(54)	(239)	(220)	(217)
Income (Loss) Before Income Tax Expense (Benefit)	97	175	83	74	45	144	73	59	429	321	336
Income Tax (Benefit) Expense	39	65	30	185	11	57	26	9	319	103	114
Net (Loss) Income from continuing operations	58	110	53	(111)	34	87	47	50	110	218	222
(Loss) Income from Discontinued Operations, net of taxes		8	(11)	(319)	9	25	15	18	(322)	67	35
Net (loss) income	58	118	42	(430)	43	112	62	68	(212)	285	257
Basic and Diluted Earnings Per Share of Common Stock
(Loss) Earnings Per Share of Common Stock from Continuing Operations	$ 0.23	$ 0.44	$ 0.21	$ (0.47)					$ 0.45
(Loss) Earnings Per Share of Common Stock from Discontinued Operations		$ 0.04	$ (0.04)	$ (1.35)					$ (1.31)
(Loss) Earnings Per Share of Common Stock	$ 0.23	$ 0.48	$ 0.17	$ (1.82)					$ (0.86)
Cash Dividends Per Share of Common Stock	$ 0.27	$ 0.27	$ 0.27	$ 0.27	$ 0.27	$ 0.27	$ 0.27	$ 0.27	$ 1.08	$ 1.08	$ 1.08
Basic Earnings Per Share of Common Stock
Earnings Per Share of Common Stock from Continuing Operations					$ 0.15	$ 0.38	$ 0.20	$ 0.22	$ 0.45	$ 0.95	$ 0.98
Earnings Per Share of Common Stock from Discontinued Operations					$ 0.03	$ 0.11	$ 0.07	$ 0.08	$ (1.31)	$ 0.30	$ 0.16
Basic Earnings Per Share of Common Stock					$ 0.18	$ 0.49	$ 0.27	$ 0.30	$ (0.86)	$ 1.25	$ 1.14
Diluted Earnings Per Share of Common Stock
Earnings Per Share of Common Stock from Continuing Operations					$ 0.15	$ 0.38	$ 0.20	$ 0.22	$ 0.45	$ 0.95	$ 0.98
Earnings Per Share of Common Stock from Discontinued Operations					$ 0.03	$ 0.11	$ 0.07	$ 0.08	$ (1.31)	$ 0.29	$ 0.16
Diluted Earnings Per Share of Common Stock					$ 0.18	$ 0.49	$ 0.27	$ 0.30	$ (0.86)	$ 1.24	$ 1.14
Cash Dividends Per Share of Common Stock	$ 0.27	$ 0.27	$ 0.27	$ 0.27	$ 0.27	$ 0.27	$ 0.27	$ 0.27	$ 1.08	$ 1.08	$ 1.08
Potomac Electric Power Co [Member]
Quarterly Financial Information [Line Items]
Total Operating Expenses	410	476	389	430	390	475	401	425	1,705	1,691	1,866
Operating Income	65	129	80	47	55	107	55	40	321	257	212
Other Expenses	(24)	(23)	(23)	(22)	(20)	(22)	(20)	(21)	(92)	(83)	(77)
Income (Loss) Before Income Tax Expense (Benefit)	41	106	57	25	35	85	35	19	229	174	135
Income Tax (Benefit) Expense	17	40	20	2	10	35	8		79	48	36
Net (loss) income	24	66	37	23	25	50	27	24	150	126	99
Diluted Earnings Per Share of Common Stock
Operating Revenue	475	605	469	477	445	582	456	465	2,026	1,948	2,078
Atlantic City Electric Co [Member]
Quarterly Financial Information [Line Items]
Total Operating Expenses	229	341	242	254	364	246	230	239	1,066	1,079	1,129
Operating Income	29	55	29	23	49	13	40	17	136	119	139
Other Expenses	(15)	(17)	(18)	(17)	(16)	(17)	(17)	(16)	(67)	(66)	(67)
Income (Loss) Before Income Tax Expense (Benefit)	14	38	11	6	33	(4)	23	1	69	53	72
Income Tax (Benefit) Expense	5	13	4	(3)	13	(3)	9	(1)	19	18	33
Net (loss) income	9	25	7	9	20	(1)	14	2	50	35	39
Diluted Earnings Per Share of Common Stock
Operating Revenue	258	396	271	277	413	259	270	256	1,202	1,198	1,268
Delmarva Power & Light Co/De [Member]
Quarterly Financial Information [Line Items]
Total Operating Expenses	258	249	235	317	263	297	229	290	1,059	1,079	1,155
Operating Income	54	47	31	53	38	43	30	43	185	154	149
Other Expenses	(9)	(10)	(10)	(11)	(11)	(10)	(8)	(8)	(40)	(37)	(36)
Income (Loss) Before Income Tax Expense (Benefit)	45	37	21	42	27	33	22	35	145	117	113
Income Tax (Benefit) Expense	17	14	9	16	10	11	9	14	56	44	42
Net (loss) income	28	23	12	26	17	22	13	21	89	73	71
Diluted Earnings Per Share of Common Stock
Operating Revenue	$ 312	$ 296	$ 266	$ 370	$ 301	$ 340	$ 259	$ 333	$ 1,244	$ 1,233	$ 1,304