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] Undistributed Earnings [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] Undistributed Earnings [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, 2015	[1]					$ (2,624)						$ (63)											$ 1
Beginning balance at Dec. 31, 2015	[1]					(2,624)						(63)											1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		$ 430							$ 285						$ 260					$ 224					$ 135						$ (60)			$ (60)			$ (97)
Other Comprehensive Income (Loss), Net of Tax		$ 59				59	[1]		(2)			(2)	[1]										0	[1]
Proceeds from Contributions from Parent															113										21						187			113			139
Ending balance at Jun. 30, 2016	[1]					(2,565)						(65)											1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Successor [Member]																												$ (257)
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																												0
Proceeds from Contributions from Parent | Successor [Member]																												1,088
Ending balance at Jun. 30, 2016	[1]					(2,565)						(65)											1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings, Appropriated															(2,626)
Beginning Balance (in shares) at Dec. 31, 2016		958,778
Beginning balance at Dec. 31, 2016		$ 27,612	$ 18,794	$ (2,327)	$ 12,030	(2,660)	[1]	$ 1,775				(54)	[1]										1	[1]
Beginning Balance at Dec. 31, 2016		25,837													8,725	$ 1,588	$ 6,150	$ (1,639)	$ 2,626	3,415	$ 2,473	$ 941	1		2,848	$ 1,421	$ 1,427				2,300	$ 1,309	$ 991	1,326	$ 764	$ 562	1,034	$ 912	$ 122
Beginning Balance (Successor [Member]) at Dec. 31, 2016																												8,016	$ 8,077	$ (61)
Beginning Balance at Dec. 31, 2016									13,256	$ 9,261	$ 2,275	(54)		$ 1,774
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Successor [Member]																												205		205
Net income		1,046	0	0	1,076	0		(30)	144		174	0		(30)	259			259		215		215			169		169				101	0	101	76		76	36		36
Stock Issued During Period, Value, Treasury Stock Reissued		$ (1,150)		(2,204)	(1,054)
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Paid									49	49
Stock Issued During Period, Shares, Share-based Compensation, Gross		2,494
Stock Issued During Period, Value, Share-based Compensation, Gross		$ 23	23	0	0	0		0
Stock Issued During Period, Shares, Employee Stock Purchase Plans		648
Stock Issued During Period, Value, Employee Stock Purchase Plan		$ 43	43	0	0	0		0
Noncontrolling Interest, Period Increase (Decrease)		1	0	0	0	0		1
Noncontrolling Interest, Increase from Sale of Parent Equity Interest									1					1
Income Tax Effects Allocated Directly to Equity, Other									(2)	(2)
Common stock dividends		(610)	0	0	(610)	0		0												(144)	0	(144)	0		(99)		(99)				(58)	0	(58)	(54)		(54)	(22)		(22)
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																												0
Other Comprehensive Income (Loss), Net of Tax		25	0	0	0	27	[1]	(2)	12		0	14	[1]	(2)									0	[1]
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared | Successor [Member]																												(131)		131
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared									(330)		(330)
Employee stock purchase plan issuances		$ 43	43	0	0	0		0
Dividends															(211)				(211)
Adjustments to Additional Paid in Capital, Other															184		184
Proceeds from Contributions from Parent | Successor [Member]																												751	751
Proceeds from Contributions from Parent															184										0						161	161		0			0
Ending Balance (in shares) at Jun. 30, 2017		961,920
Ending balance at Jun. 30, 2017		$ 29,290	$ 18,860	$ (123)	$ 11,442	$ (2,633)	[1]	$ 1,744				(40)	[1]										1	[1]
Ending Balance at Jun. 30, 2017		$ 27,546													8,980	$ 1,588	6,357	(1,639)	2,674	$ 3,486	$ 2,473	$ 1,012	$ 1		$ 2,918	$ 1,421	$ 1,497				$ 2,504	$ 1,470	$ 1,034	$ 1,348	$ 764	$ 584	$ 1,048	$ 912	$ 136
Ending Balance (Successor [Member]) at Jun. 30, 2017																												$ 8,841	$ 8,828	$ 13
Ending Balance at Jun. 30, 2017									$ 13,130	$ 9,308	$ 2,119	$ (40)		$ 1,743
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings, Appropriated															(2,674)			$ (259)	$ (259)
Other Additional Capital															$ 23		$ 23

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