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 Earnings, 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 Additional Capital [Member]	Commonwealth Edison Co [Member] Retained Earnings, 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 Earnings, 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 at Dec. 31, 2016	[1]					$ (2,660)
Beginning Balance at Dec. 31, 2016	[1]											$ (54)
Beginning Balance at Dec. 31, 2016	[1]																						$ 1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		$ 1,066							$ 164						$ 259					$ 215					$ 169			$ 205			$ 101			$ 76			$ 36
Other Comprehensive Income (Loss), Net of Tax		$ 25				27	[1]		12			14	[1]										0	[1]
Ending balance at Jun. 30, 2017	[1]					(2,633)
Ending Balance at Jun. 30, 2017	[1]											(40)
Ending Balance at Jun. 30, 2017	[1]																						1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings, Appropriated															(2,771)
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)	[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		29,896													9,542	$ 1,588	$ 6,822	$ (1,639)	$ 2,771	3,577	$ 2,489	$ 1,087	1	[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			1,125			54	368		314	0		54	329			329		210	0	210	0		179		179	149	0	149	85		85	57		57	15		15
Stock Issued During Period, Shares, Share-based Compensation, Gross		1,868
Stock Issued During Period, Value, Share-based Compensation, Gross		$ 17	17	0	0	0		0
Stock Issued During Period, Shares, Employee Stock Purchase Plans		703
Stock Issued During Period, Value, Employee Stock Purchase Plan		$ 27	27	0	0	0		0
Noncontrolling Interest, Period Increase (Decrease)		(23)						(23)	(23)					(23)
Common stock dividends		(669)			(669)										(229)				(229)	(293)	0	(293)	0		(105)		(105)				(50)		(50)	(40)		(40)	(19)		(19)
Equity Contribution																				41	41
Other Comprehensive Income (Loss), Net of Tax		117				115	[1]	2	9		0	7	[1]	2									0	[1]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		$ 4			14	(10)			3		6	(3)								0		1	(1)
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared									(377)		(377)																	(109)	0	(109)
Adjustments to Additional Paid in Capital, Other															225		225											235	235	0	85	85		150	150
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)	[1]	$ 2,324
Ending Balance at Jun. 30, 2018									$ 15,939	$ 9,357	$ 4,292	$ (33)	[1]	$ 2,323														$ 9,100	$ 9,070	$ 30
Ending Balance at Jun. 30, 2018		$ 30,515													9,867	$ 1,588	$ 7,047	(1,639)	2,871	$ 3,535	$ 2,530	$ 1,005	$ 0	[1]	$ 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]
Retained Earnings, Appropriated															$ (2,871)			$ (329)	$ (329)

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