Consolidated Statements of Changes in Shareholders Equity (Unaudited) - USD ($) shares in Thousands, $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Other Comprehensive Income (Loss) [Member]	Exelon Generation Co L L C [Member]	Exelon Generation Co L L C [Member] Membership Interest [Member]	Exelon Generation Co L L C [Member] Retained Earnings, Unappropriated/Undistributed [Member]	Exelon Generation Co L L C [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Exelon Generation Co L L C [Member] Noncontrolling Interest [Member]	Commonwealth Edison Co [Member]	Commonwealth Edison Co [Member] Common Stock [Member]	Commonwealth Edison Co [Member] Other Paid-in-Capital [Member]	Commonwealth Edison Co [Member] Retained Earnings, Unappropriated/Undistributed [Member]	Commonwealth Edison Co [Member] Retained Earnings, Appropriated	Commonwealth Edison Co [Member] Retained Earnings [Member]	PECO Energy Co [Member]	PECO Energy Co [Member] Common Stock [Member]	PECO Energy Co [Member] Retained Earnings [Member]	PECO Energy Co [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Baltimore Gas and Electric Company [Member]	Baltimore Gas and Electric Company [Member] Common Stock [Member]	Baltimore Gas and Electric Company [Member] Retained Earnings [Member]	Pepco Holdings LLC [Member]	Pepco Holdings LLC [Member] Membership Interest [Member]	Pepco Holdings LLC [Member] Retained Earnings, Unappropriated/Undistributed [Member]	Potomac Electric Power Company [Member]	Potomac Electric Power Company [Member] Common Stock [Member]	Potomac Electric Power Company [Member] Retained Earnings [Member]	Delmarva Power and Light Company [Member]	Delmarva Power and Light Company [Member] Common Stock [Member]	Delmarva Power and Light Company [Member] Retained Earnings [Member]	Atlantic City Electric Company [Member]	Atlantic City Electric Company [Member] Common Stock [Member]	Atlantic City Electric Company [Member] Retained Earnings [Member]
Beginning balance (in shares) at Dec. 31, 2017	965,168
Beginning balance at Dec. 31, 2017	$ 32,187	$ 18,964	$ (123)	$ 14,081	$ (3,026)	$ 2,291
Beginning Balance at Dec. 31, 2017								$ 15,959	$ 9,357	$ 4,349	$ (37)	$ 2,290														$ 8,825	$ 8,835	$ (10)
Beginning Balance at Dec. 31, 2017													$ 9,542	$ 1,588	$ 6,822	$ (1,639)	$ 2,771		$ 3,577	$ 2,489	$ 1,087	$ 1	$ 3,141	$ 1,605	$ 1,536				$ 2,533	$ 1,470	$ 1,063	$ 1,335	$ 764	$ 571	$ 1,043	$ 912	$ 131
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 636			585		51		186		136		50	165			165			113		113	0	128		128	65		65	31		31	31		31	7		7
Stock issued during period, shares, long-term incentive plan activity	1,685
Stock issued during period, value, long-term incentive plan activity	$ (3)	(3)	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	361
Stock issued during period, value, employee stock purchase plan	$ 12	12	0	0	0	0
Changes in equity of noncontrolling interests	(9)					(9)		(9)				(9)
Common stock dividends	(334)			(334)									(114)				(114)		(287)		(287)		(52)		(52)				(25)		(25)	(36)		(36)	(9)		(9)
Distributions to member								(188)		(188)																(71)		(71)
Contributions from parent													113	0	113
Other comprehensive income (loss), net of income taxes					71	1	$ 72	7		0	6	1
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard	$ 4			14	(10)			3		6	(3)								0		1	(1)
Ending balance (in shares) at Mar. 31, 2018	967,214
Ending balance at Mar. 31, 2018	$ 32,565	18,973	(123)	14,346	(2,965)	2,334
Ending Balance at Mar. 31, 2018								15,958	9,357	4,303	(34)	2,332														8,819	8,835	(16)
Ending Balance at Mar. 31, 2018													9,706	1,588	6,935	(1,639)	2,822		3,403	2,489	914	0	3,217	1,605	1,612				2,539	1,470	1,069	1,330	764	566	1,041	912	129
Beginning balance (in shares) at Dec. 31, 2017	965,168
Beginning balance at Dec. 31, 2017	$ 32,187	18,964	(123)	14,081	(3,026)	2,291
Beginning Balance at Dec. 31, 2017								15,959	9,357	4,349	(37)	2,290														8,825	8,835	(10)
Beginning Balance at Dec. 31, 2017													9,542	1,588	6,822	(1,639)	2,771		3,577	2,489	1,087	1	3,141	1,605	1,536				2,533	1,470	1,063	1,335	764	571	1,043	912	131
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,179							368					329						210				179			149			85			57			15
Other comprehensive income (loss), net of income taxes	$ 117				115			9			7
Ending balance (in shares) at Jun. 30, 2018	967,739
Ending balance at Jun. 30, 2018	$ 32,839	19,008	(123)	14,551	(2,921)	2,324
Ending Balance at Jun. 30, 2018								15,939	9,357	4,292	(33)	2,323														9,100	9,070	30
Ending Balance at Jun. 30, 2018													9,867	1,588	7,047	(1,639)	2,871		3,535	2,530	1,005	0	3,215	1,605	1,610				2,653	1,555	1,098	1,502	914	588	1,039	912	127
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends																(165)	165	$ 0
Beginning balance (in shares) at Mar. 31, 2018	967,214
Beginning balance at Mar. 31, 2018	$ 32,565	18,973	(123)	14,346	(2,965)	2,334
Beginning Balance at Mar. 31, 2018								15,958	9,357	4,303	(34)	2,332														8,819	8,835	(16)
Beginning Balance at Mar. 31, 2018													9,706	1,588	6,935	(1,639)	2,822		3,403	2,489	914	0	3,217	1,605	1,612				2,539	1,470	1,069	1,330	764	566	1,041	912	129
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 542			539		3		181		178		3	164			164			96		96	0	51		51	84		84	54		54	26		26	8		8
Stock issued during period, shares, long-term incentive plan activity	183
Stock issued during period, value, long-term incentive plan activity	$ 20	20	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	342
Stock issued during period, value, employee stock purchase plan	$ 15	15	0	0	0	0
Changes in equity of noncontrolling interests	(14)					(14)		(13)				(13)
Common stock dividends	(334)			(334)									(115)				(115)		(5)		(5)		(53)		(53)				(25)		(25)	(4)		(4)	(10)		(10)
Distributions to member								(189)		(189)																(38)		(38)
Contributions from parent													112	0	112				41	41	0	0				235	235		85	85		150	150
Other comprehensive income (loss), net of income taxes	$ 44				44	1	45	2		0	1	1
Ending balance (in shares) at Jun. 30, 2018	967,739
Ending balance at Jun. 30, 2018	$ 32,839	19,008	(123)	14,551	(2,921)	2,324
Ending Balance at Jun. 30, 2018								15,939	9,357	4,292	(33)	2,323														9,100	9,070	30
Ending Balance at Jun. 30, 2018													9,867	1,588	7,047	(1,639)	2,871		3,535	2,530	1,005	0	3,215	1,605	1,610				2,653	1,555	1,098	1,502	914	588	1,039	912	127
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends																(164)	164	0
Appropriation of retained earnings for future dividends													2,976
Beginning balance (in shares) at Dec. 31, 2018	970,020
Beginning balance at Dec. 31, 2018	$ 33,070	19,116	(123)	14,766	(2,995)	2,306
Beginning Balance at Dec. 31, 2018								15,508	9,518	3,724	(38)	2,304														9,282	9,220	62
Beginning Balance at Dec. 31, 2018	30,764												10,247	1,588	7,322	(1,639)	2,976		3,820	2,578	1,242	0	3,354	1,714	1,640				2,740	1,636	1,104	1,509	914	595	1,126	979	147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 966			907		59		422		363		59	157			157			168		168	0	160		160	117		117	55		55	53		53	10		10
Stock issued during period, shares, long-term incentive plan activity	2,446
Stock issued during period, value, long-term incentive plan activity	$ (3)	(3)	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	320
Stock issued during period, value, employee stock purchase plan	$ 51	51	0	0	0	0
Changes in equity of noncontrolling interests	(17)					(17)		(17)				(17)
Sale of noncontrolling interests	7	7						7	7
Common stock dividends	$ (352)			(352)									(127)				(127)		(90)		(90)		(56)		(56)				(24)		(24)	(41)		(41)	(12)		(12)
Distributions to member								(225)		(225)																(128)		(128)
Contributions from parent													63	0	63				145	145	0	0				19	19		14	14					5	5
Other comprehensive income (loss), net of income taxes					(17)	(1)	(18)	1		0	2	(1)
Ending balance (in shares) at Mar. 31, 2019	972,786
Ending balance at Mar. 31, 2019	$ 33,704	19,171	(123)	15,321	(3,012)	2,347
Ending Balance at Mar. 31, 2019								15,696	9,525	3,862	(36)	2,345														9,290	9,239	51
Ending Balance at Mar. 31, 2019													10,340	1,588	7,385	(1,639)	3,006		4,043	2,723	1,320	0	3,458	1,714	1,744				2,785	1,650	1,135	1,521	914	607	1,129	984	145
Beginning balance (in shares) at Dec. 31, 2018	970,020
Beginning balance at Dec. 31, 2018	$ 33,070	19,116	(123)	14,766	(2,995)	2,306
Beginning Balance at Dec. 31, 2018								15,508	9,518	3,724	(38)	2,304														9,282	9,220	62
Beginning Balance at Dec. 31, 2018	30,764												10,247	1,588	7,322	(1,639)	2,976		3,820	2,578	1,242	0	3,354	1,714	1,640				2,740	1,636	1,104	1,509	914	595	1,126	979	147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,460							540					344						270				206			223			119			83			24
Other comprehensive income (loss), net of income taxes	$ 3				5			0			2
Ending balance (in shares) at Jun. 30, 2019	973,417
Ending balance at Jun. 30, 2019	$ 33,907	19,209	(123)	15,452	(2,990)	2,359
Ending Balance at Jun. 30, 2019								15,592	9,525	3,746	(36)	2,357														9,572	9,503	69
Ending Balance at Jun. 30, 2019	$ 31,548												10,460	1,588	7,446	(1,639)	3,065		4,055	2,723	1,332	0	3,448	1,714	1,734				2,916	1,765	1,151	1,522	914	608	1,281	1,134	147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends																(157)	157	0
Beginning balance (in shares) at Mar. 31, 2019	972,786
Beginning balance at Mar. 31, 2019	$ 33,704	19,171	(123)	15,321	(3,012)	2,347
Beginning Balance at Mar. 31, 2019								15,696	9,525	3,862	(36)	2,345														9,290	9,239	51
Beginning Balance at Mar. 31, 2019													10,340	1,588	7,385	(1,639)	3,006		4,043	2,723	1,320	0	3,458	1,714	1,744				2,785	1,650	1,135	1,521	914	607	1,129	984	145
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 494			484		10		118		108		10	186			186			102		102	0	45		45	106		106	64		64	30		30	14		14
Stock issued during period, shares, long-term incentive plan activity	320
Stock issued during period, value, long-term incentive plan activity	$ 14	14	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	311
Stock issued during period, value, employee stock purchase plan	$ 24	24	0	0	0	0
Changes in equity of noncontrolling interests	3					3		3				3
Sale of noncontrolling interests	0	0
Common stock dividends	(353)			(353)									(127)				(127)		(90)		(90)		(55)		(55)				(48)		(48)	(29)		(29)	(12)		(12)
Distributions to member								(224)		(224)																(88)		(88)
Contributions from parent													61	0	61				0	0	0	0				264	264		115	115					150	150
Other comprehensive income (loss), net of income taxes	$ 21				22	(1)	$ 21	(1)		0	0	(1)
Ending balance (in shares) at Jun. 30, 2019	973,417
Ending balance at Jun. 30, 2019	$ 33,907	$ 19,209	$ (123)	$ 15,452	$ (2,990)	$ 2,359
Ending Balance at Jun. 30, 2019								$ 15,592	$ 9,525	$ 3,746	$ (36)	$ 2,357														$ 9,572	$ 9,503	$ 69
Ending Balance at Jun. 30, 2019	$ 31,548												10,460	$ 1,588	$ 7,446	(1,639)	3,065		$ 4,055	$ 2,723	$ 1,332	$ 0	$ 3,448	$ 1,714	$ 1,734				$ 2,916	$ 1,765	$ 1,151	$ 1,522	$ 914	$ 608	$ 1,281	$ 1,134	$ 147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends													$ 3,065			$ (186)	$ 186	$ 0