Consolidated Statements of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Exelon Generation Co L L C [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member]	Sep. 30, 2014 Commonwealth Edison Co [Member]	Sep. 30, 2013 Commonwealth Edison Co [Member]	Sep. 30, 2014 PECO Energy Co [Member]	Sep. 30, 2013 PECO Energy Co [Member]	Sep. 30, 2014 Baltimore Gas and Electric Company [Member]	Sep. 30, 2013 Baltimore Gas and Electric Company [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	$ 1,725	$ 1,235	$ 1,037	$ 795	$ 335	$ 140	$ 255	$ 292	$ 156	$ 160
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	2,856	2,844	1,853	1,937	521	501	176	171	275	252
Impairment of long-lived assets	162	171	138	157
Gain on consolidation of CENG	(268)	0	(268)	0
Gain on sale of assets	(356)	(17)	(355)	(13)
Deferred income taxes and amortization of investment tax credits	459	(164)	154	183	154	(152)	7	35	57	105
Net fair value changes related to derivatives	522	(229)	509	(222)
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(141)	(95)	(141)	(95)
Other non-cash operating activities	698	584	251	231	116	26	70	84	129	105
Changes in assets and liabilities:
Accounts receivable	198	54	153	57	(109)	(21)	63	41	101	(28)
Receivables from and payables to affiliates, net			72	2	(55)	(32)	(20)	(25)	(11)	(12)
Inventories	(316)	(103)	(286)	(81)	(12)	(12)	5	4	(21)	(15)
Accounts payable, accrued expenses and other current liabilities	(322)	(243)	(311)	(162)	59	48	19	9	(50)	(5)
Option premiums received (paid), net	21	(38)	21	(38)
Counterparty collateral posted, net	(615)	(73)	(634)	(123)					16	0
Income taxes	72	863	172	315	15	262	16	66	53	6
Pension and non-pension postretirement benefit contributions	(516)	(360)	(214)	(123)	(237)	(120)	(12)	(10)	(13)	(16)
Other assets and liabilities	(536)	(35)	(367)	(163)	62	210	(75)	(47)	(67)	(119)
Net cash flows provided by operating activities	3,643	4,394	1,784	2,657	849	850	504	620	625	433
Cash flows from investing activities
Capital expenditures	(4,114)	(3,887)	(1,961)	(1,995)	(1,173)	(1,074)	(461)	(374)	(458)	(391)
Proceeds from nuclear decommissioning trust fund sales	5,464	3,344	5,464	3,344
Investment in nuclear decommissioning trust funds	(5,550)	(3,518)	(5,550)	(3,518)
Acquisition of businesses	(67)	0	(67)	0
Changes in intercompany money pool							0	(1)
Proceeds from sale of long-lived assets	660	32	660	32
Proceeds from termination of direct financing lease investment	335	0
Proceeds from sale of investments	7	20			7	5
Purchases of investments	(3)	(3)			(3)	(3)
Cash consolidated from CENG	129	0	129	0
Change in restricted cash	(151)	(23)	(116)	(30)	(2)	(3)	0	(1)	(37)	(20)
Other investing activities	(86)	65	(34)	18	23	33	9	8	15	2
Changes in Exelon intercompany money pool			44	0
Net cash flows used in investing activities	(3,376)	(3,970)	(1,431)	(2,149)	(1,148)	(1,042)	(452)	(368)	(480)	(409)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Payment of accounts receivable agreement	0	(210)
Changes in short-term borrowings	236	205	7	12	344	153			(115)	40
Issuance of long-term debt	3,212	2,031	1,112	831	650	350	300	550	0	300
Retirement of long-term debt	(1,214)	(1,156)	(552)	(471)	(617)	(252)			(35)	(433)
Redemption of preferred securities	0	(93)					0	(93)
Distributions to noncontrolling interest of consolidated VIE	(415)	0	(415)	0
Dividends paid on common stock	(799)	(981)			(230)	(165)	(240)	(248)
Proceeds from employee stock plans	25	40
Other financing activities	(158)	(102)	(67)	(73)	(8)	(4)	(7)	(3)	11	(3)
Payment of accounts receivable agreement							0	(210)
Distribution to member			(440)	(550)
Contributions from parent					168	0	24	0	0
Dividends paid on preferred securities							0	(1)	(10)	(10)
Contribution from member			55	0
Net cash flows provided by (used in) financing activities	887	(266)	(300)	(251)	307	82	77	(5)	(149)	(106)
Increase in cash and cash equivalents	1,154	158	53	257	8	(110)	129	247	(4)	(82)
Cash and cash equivalents at beginning of period	1,609	1,486	1,258	671	36	144	217	362	31	89
Cash and cash equivalents at end of period	$ 2,763	$ 1,644	$ 1,311	$ 928	$ 44	$ 34	$ 346	$ 609	$ 27	$ 7