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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		$ 123							$ 257						$ 115					$ 124					$ 101						$ (108)			$ (72)			$ (100)
Other Comprehensive Income (Loss), Net of Tax		$ 28				28	[1]		(1)			(1)	[1]										0
Proceeds from Contributions from Parent															39										21
Ending Balance at Mar. 31, 2016	[1]					(2,596)						(64)											1
Beginning Balance at Dec. 31, 2015	[1]					(2,624)						(63)											1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Successor [Member]																												$ (309)
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																												0
Proceeds from Contributions from Parent | Successor [Member]																												0
Ending Balance at Mar. 31, 2016	[1]					(2,596)						(64)											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]																												140		140
Net income		$ 981	0	0	995	0		(14)	409		423	0		(14)	141			141		127		127			125		125				58		58	57		57	28		28
Stock Issued During Period, Shares, Share-based Compensation, Gross		1,739
Stock Issued During Period, Value, Share-based Compensation, Gross		$ 1	1	0	0	0		0
Stock Issued During Period, Shares, Employee Stock Purchase Plans		323
Stock Issued During Period, Value, Employee Stock Purchase Plan		$ 12	12	0	0	0		0
Noncontrolling Interest, Period Increase (Decrease)		2	0	0	0	0		2
Noncontrolling Interest, Increase from Sale of Parent Equity Interest									3					3
Income Tax Effects Allocated Directly to Equity, Other									49	(49)
Common stock dividends		(305)	0	0	(305)	0		0												(72)		(72)			(49)		(49)							(30)		(30)	(10)		(10)
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																												0
Other Comprehensive Income (Loss), Net of Tax		(12)	0	0	0	(10)	[1]	(2)	11		0	13	[1]	(2)									0	[1]
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared | Successor [Member]																												(69)		69
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared											(164)
Employee stock purchase plan issuances		$ 12	12	0	0	0		0
Adjustments to Additional Paid in Capital, Other | Successor [Member]																												500
Adjustments to Additional Paid in Capital, Other															100		100
Dividends															(105)				(105)												(30)		(30)
Proceeds from Contributions from Parent | Successor [Member]																												500	500
Proceeds from Contributions from Parent															100										0
Ending Balance (in shares) at Mar. 31, 2017		960,840
Ending Balance at Mar. 31, 2017		$ 28,291	$ 18,807	$ (2,327)	$ 12,720	$ (2,670)	[1]	$ 1,761				(41)	[1]										1	[1]
Ending Balance at Mar. 31, 2017		$ 26,530													8,861	$ 1,588	$ 6,250	(1,639)	2,662	$ 3,470	$ 2,473	$ 996	$ 1		$ 2,924	$ 1,421	$ 1,503				$ 2,328	$ 1,309	$ 1,019	$ 1,353	$ 764	$ 589	$ 1,052	$ 912	$ 140
Ending Balance (Successor [Member]) at Mar. 31, 2017																												$ 8,587	$ 8,577	$ 10
Ending Balance at Mar. 31, 2017									$ 13,564	$ 9,310	$ 2,534	$ (41)		$ 1,761
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings, Appropriated															$ (2,662)			$ (141)	$ (141)

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