Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Statements of Cash Flows (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net cash flows provided by operating activities	$ 4,457	$ 6,343	$ 6,131
Cash flows from investing activities
Proceeds from termination of direct financing lease investment	335	0	0
Capital expenditures	(6,077)	(5,395)	(5,789)
Cash and restricted cash acquired from Constellation	140	0	964
Change in restricted cash	(104)	(43)	(34)
Other investing activities	(88)	112	136
Net cash flows used in investing activities	(4,599)	(5,394)	(4,576)
Cash flows from financing activities
Changes in short-term borrowings	122	332	(197)
Issuance of long-term debt	3,463	2,055	2,027
Retirement of long-term debt	(1,545)	(1,589)	(1,145)
Dividends paid on common stock	(1,065)	(1,249)	(1,716)
Proceeds from employee stock plans	35	47	72
Other financing activities	(178)	(119)	(111)
Net cash flows provided by (used in) financing activities	411	(826)	(1,085)
Increase in cash and cash equivalents	269	123	470
Cash and cash equivalents at beginning of period	1,609	1,486	1,016
Cash and cash equivalents at end of period	1,878	1,609	1,486
Exelon Corporate [Member]
Net cash flows provided by operating activities	806	1,053	2,131
Cash flows from investing activities
Proceeds from termination of direct financing lease investment	335	0	0
Changes in Exelon intercompany money pool	(83)	(60)	0
Note receivable from affiliates	0	484	0
Capital expenditures	1	0	(30)
Cash and restricted cash acquired from Constellation	0	0	679
Change in restricted cash	0	38	(38)
Investment in affiliates	(70)	(38)	(67)
Other investing activities	(126)	15	0
Net cash flows used in investing activities	57	439	544
Cash flows from financing activities
Changes in Exelon intercompany money pool	0	0	(703)
Changes in short-term borrowings	0	10	(161)
Issuance of long-term debt	1,150	0	0
Retirement of long-term debt	(23)	(450)	(77)
Dividends paid on common stock	(1,065)	(1,249)	(1,716)
Proceeds from employee stock plans	35	47	73
Other financing activities	(84)	(6)	30
Net cash flows provided by (used in) financing activities	13	(1,648)	(2,554)
Increase in cash and cash equivalents	876	(156)	121
Cash and cash equivalents at beginning of period	3	159	38
Cash and cash equivalents at end of period	$ 879	$ 3	$ 159