Consolidated Statement 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]	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/Undistributed Earnings (Losses), Unappropriated [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/Undistributed Earnings (Losses), Unappropriated [Member]	Commonwealth Edison Co [Member] Retained Earnings, Appropriated [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/Undistributed Earnings (Losses), Unappropriated [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	965,168,000
Beginning balance at Dec. 31, 2017	$ 32,187	$ 18,964	$ (123)	$ 14,081	$ (3,026)	[1]	$ 2,291
Beginning Balance at Dec. 31, 2017								$ 15,959	$ 9,357	$ 4,349	$ (37)	[1]	$ 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	0		50	165			165		113		113		128		128	65		65	31		31	31		31	7		7
Stock issued during period, shares, long-term incentive plan activity	1,685,000
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	361,000
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)
Contributions from parent														113		113
Distributions to member								(188)		(188)																(71)		(71)
Other comprehensive income (loss), net of income taxes	72				71	[1]	1	7		0	6	[1]	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	967,214,000
Ending balance at Mar. 31, 2018	$ 32,565	18,973	(123)	14,346	(2,965)	[1]	2,334
Ending Balance at Mar. 31, 2018								15,958	9,357	4,303	(34)	[1]	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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends																	(165)	165
Appropriation of retained earnings for future dividends														(2,976)
Beginning balance (in shares) at Dec. 31, 2018	970,020,000
Beginning balance at Dec. 31, 2018	$ 33,070	19,116	(123)	14,766	(2,995)	[1]	2,306
Beginning Balance at Dec. 31, 2018								15,508	9,518	3,724	(38)	[1]	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	0		59	157			157		168		168		160		160	117		117	55		55	53		53	10		10
Stock issued during period, shares, long-term incentive plan activity	2,446,000
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	320,000
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)
Contributions from parent														63		63			(145)	(145)						19	19		14	14					5	5
Distributions to member								(225)		(225)																(128)		(128)
Other comprehensive income (loss), net of income taxes	$ (18)				(17)	[1]	(1)	1		0	2	[1]	(1)
Ending balance (in shares) at Mar. 31, 2019	972,786,000
Ending balance at Mar. 31, 2019	$ 33,704	$ 19,171	$ (123)	$ 15,321	$ (3,012)	[1]	$ 2,347
Ending Balance at Mar. 31, 2019								$ 15,696	$ 9,525	$ 3,862	$ (36)	[1]	$ 2,345													$ 9,290	$ 9,239	$ 51
Ending Balance at Mar. 31, 2019	$ 31,357													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]
Appropriation of retained earnings for future dividends														$ (3,006)			$ (157)	$ 157

[1] All amounts are net of tax and noncontrolling interests. Amounts in parenthesis represent a decrease in AOCI.