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]	Preference Stock Not Subject To Mandatory Redemption [Member]	Exelon Generation Co L L C [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]	Exelon Generation Co L L C [Member] Membership Interest [Member]	Commonwealth Edison Co [Member]	Commonwealth Edison Co [Member] Common Stock [Member]	Commonwealth Edison Co [Member] Retained Earnings, Unappropriated [Member]	Commonwealth Edison Co [Member] Retained Earnings, Appropriated [Member]	Commonwealth Edison Co [Member] Other Additional Capital [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]	Baltimore Gas and Electric Company [Member] Preferred Stock [Member]	Pepco Holdings LLC [Member]	Pepco Holdings LLC [Member] Additional Paid-in Capital [Member]	Pepco Holdings LLC [Member] Common Stock [Member]	Pepco Holdings LLC [Member] Retained Earnings [Member]	Pepco Holdings LLC [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Pepco Holdings LLC [Member] Common Stock Including Additional Paid in Capital [Member]	Pepco Holdings LLC [Member] Membership Interest [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]	Pepco Holdings LLC [Member]	Pepco Holdings LLC [Member] Common Stock Including Additional Paid in Capital [Member]	Deferred Compensation, Share-based Payments [Member] Pepco Holdings LLC [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated other comprehensive loss, net	[1]	$ (2,684)									$ (36)												$ 1
Other Comprehensive Income (Loss), Net of Tax | Predecessor [Member]																																$ 5
Other Comprehensive Income (Loss), Net of Tax	[1]	88									(24)												0
Net income | Predecessor [Member]																																197
Net income		1,959									1,208							$ 339					299					$ 212											$ 128			$ 55			$ 37
Proceeds from Contributions from Parent | Predecessor [Member]																																0
Proceeds from Contributions from Parent																		75					16					6											112			75			0
Payments to Acquire Businesses, Gross		(28)									(28)
Ending Balance (Predecessor [Member]) at Dec. 31, 2015																																4,413					$ 3,832
Ending Balance at Dec. 31, 2015		$ 27,294		$ 18,676	$ (2,327)	$ 12,068	$ (2,624)		$ 1,308	$ 193																		2,877											2,240
Ending Balance (in shares) at Dec. 31, 2015		954,668
Ending Balance at Dec. 31, 2015		$ 25,793																8,243	$ 1,588	$ (1,639)	$ 2,617	$ 5,677	3,236		$ 2,455	$ 780	$ 1	2,687	$ 1,367	$ 1,320	$ 190								2,240	$ 1,122	$ 1,118	1,237	$ 612	$ 625	1,000	$ 773	$ 227
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax | Predecessor [Member]																																1
Other Comprehensive Income (Loss), Net of Tax		32									(13)
Net income | Predecessor [Member]																																91
Net income		587									332							149					90					54											60			15			22
Accumulated other comprehensive loss, net	[1]	(2,596)									(60)												1
Common Stock, Value, Issued | Predecessor [Member]																																		$ 3
Common Stock, Value, Issued		18,676																1,588					2,455					1,367											1,122			612			773
Beginning Balance | Predecessor [Member]																																3,832
Beginning Balance											8,997						$ 8,997
Retained Earnings (Accumulated Deficit) | Predecessor [Member]																																617			$ 617
Retained Earnings (Accumulated Deficit)		12,068									2,701		$ 2,701					978					780					1,320														625			227
Accumulated other comprehensive loss, net | Predecessor [Member]																																(36)				$ (36)
Accumulated other comprehensive loss, net		(2,624)	[1]								(63)	[1]		$ (63)		$ 1,307							1	[1]
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest											12,942
Additional Paid in Capital | Predecessor [Member]																																	$ 3,829
Additional Paid in Capital																		5,677																					1,118
Derivative Asset, Noncurrent | Predecessor [Member]																																0
Derivative Asset, Noncurrent		$ 758									733
Other Comprehensive Income (Loss), Net of Tax | Predecessor [Member]																																1				1
Stock Issued During Period, Value, Employee Stock Purchase Plan | Predecessor [Member]																																3					3
Net income | Predecessor [Member]																																19			19
Employee stock purchase plan issuances | Predecessor [Member]																																3					3
Ending Balance (Predecessor [Member]) at Mar. 23, 2016																																4,439			636	(35)	3,838
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from Contributions from Parent | Predecessor [Member]																																0
Beginning Balance (in shares) at Dec. 31, 2015		954,668
Beginning Balance (Predecessor [Member]) at Dec. 31, 2015																																4,413					3,832
Beginning Balance at Dec. 31, 2015		$ 27,294		18,676	(2,327)	12,068	(2,624)		1,308	193																		2,877											2,240
Beginning Balance at Dec. 31, 2015		25,793																8,243	1,588	(1,639)	2,617	5,677	3,236		2,455	780	1	2,687	1,367	1,320	190								2,240	1,122	1,118	1,237	612	625	1,000	773	227
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax		96					101	[1]			2		0	7	[1]	(5)
Net Working Capital		96		0	0	0			(5)	0
Stock Issued During Period, Value, Employee Stock Purchase Plan		$ 36		36	0	0	0		0	0
Stock Issued During Period, Shares, Employee Stock Purchase Plans		924
Net income		$ 956		0	0	930	0		18	8	556		538	0		18		297		297			346			346		191		191									20		20	(16)		(16)	(50)		(50)	$ (92)
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared											(167)		(167)															(7)	(7)	0
Noncontrolling Interest, Increase from Sale of Parent Equity Interest											105
Long-term incentive plan activity (in shares)		2,422
Long-term incentive plan activity		$ 61		61	0	0	0		0	0
Employee stock purchase plan issuances (in shares)		924
Employee stock purchase plan issuances		$ 36		36	0	0	0		0	0
Appropriation of retained earnings for future dividends																		0		(297)	297
Tax benefit on stock compensation		(17)		(17)	0	0	0		0	0
Common stock dividends		(877)		0	0	(877)	0		0	(8)								(275)			(275)		(208)			(208)		(134)		(134)												(39)		(39)	(24)		(24)
Contribution from parent											170						170	188				188						28	28	0									187	187		113	113		139	139
Dividends																																							(125)		(125)
Allocation of tax benefit from parent																		157				157	18
Minority Interest Increase From Acquisition		5		0	0	0	0		5	0	5					5
Preferred security dividends		(8)																										(8)		(8)	0
Temporary Equity, Other Changes		(107)		0	0	0	0		(107)	0	107					(107)
Allocation Of Tax Benefit From Members											98						98
Ending Balance at Sep. 30, 2016		$ 27,460		18,756	(2,327)	12,121	(2,523)		1,433	0																		2,757											2,322
Ending Balance (in shares) at Sep. 30, 2016		958,014
Ending Balance at Sep. 30, 2016		$ 26,027																8,610	1,588	(1,639)	2,639	6,022	3,392		2,473	918	1	2,757	1,388	1,369	0								2,322	1,309	1,013	1,295	725	570	1,065	912	153
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from Contributions from Parent																		188					18					28											187			113			139
Payments to Acquire Businesses, Gross | Successor [Member]																																							(33)
Payments to Acquire Businesses, Gross		(6,896)									(255)																																							$ (29)
Common Stock, Value, Issued | Predecessor [Member]																																3		$ 3			3
Additional Paid in Capital | Predecessor [Member]																																	$ 3,835
Payments to Acquire Businesses, Gross | Successor [Member]																																																(33)
Beginning Balance | Successor [Member]																																7,200					7,200
Retained Earnings (Accumulated Deficit) | Successor [Member]																																			0
Accumulated other comprehensive loss, net | Successor [Member]																																				0
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest | Successor [Member]																																7,200
Business Combination, Contingent Consideration, Asset | Successor [Member]																																(301)					235
Business Combination, Contingent Consideration, Liability, Noncurrent | Successor [Member]																																53					53
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																																0
Net income | Successor [Member]																																(91)			(91)			$ 0
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared | Successor [Member]																																					66
Contribution from parent | Successor [Member]																																1,088					1,088
Ending Balance at Sep. 30, 2016		$ 27,460		18,756	(2,327)	12,121	(2,523)		1,433	0																		2,757											2,322
Ending Balance (in shares) at Sep. 30, 2016		958,014
Ending Balance at Sep. 30, 2016		$ 26,027																8,610	1,588	(1,639)	2,639	6,022	3,392		2,473	918	1	2,757	1,388	1,369	0								2,322	1,309	1,013	1,295	725	570	1,065	912	153
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from Contributions from Parent | Successor [Member]																																1,088
Payments to Acquire Businesses, Gross | Successor [Member]																																																(62)	$ (62)	$ (29)
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																																0
Other Comprehensive Income (Loss), Net of Tax		36									4
Net income | Successor [Member]																																166
Net income		526									271							37					122					56											79			44			47			$ 169
Ending Balance at Sep. 30, 2016		$ 27,460		$ 18,756	$ (2,327)	$ 12,121	$ (2,523)		$ 1,433	0																		2,757											2,322
Ending Balance (in shares) at Sep. 30, 2016		958,014
Ending Balance at Sep. 30, 2016		$ 26,027																8,610	$ 1,588	$ (1,639)	$ 2,639	$ 6,022	3,392		$ 2,473	$ 918	$ 1	2,757	$ 1,388	$ 1,369	0								2,322	$ 1,309	$ 1,013	1,295	$ 725	$ 570	1,065	$ 912	$ 153
Common Stock, Value, Issued		18,756																1,588					2,473					1,388											1,309			725			912
Preferred Stock, Redemption Amount		193								$ 193																		(190)			$ (190)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance | Successor [Member]																																7,978					7,978
Beginning Balance											9,265						$ 9,265
Retained Earnings (Accumulated Deficit) | Successor [Member]																																(91)			$ (91)
Retained Earnings (Accumulated Deficit)		12,121									3,072		$ 3,072					1,000					918					$ 1,369														$ 570			$ 153
Accumulated other comprehensive loss, net | Successor [Member]																																0				$ 0
Accumulated other comprehensive loss, net		(2,523)	[1]								(56)	[1]		$ (56)		$ 1,432							$ 1	[1]
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest | Successor [Member]																																7,887
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest											13,713
Business Combination, Contingent Consideration, Asset | Successor [Member]																																					$ (301)
Business Combination, Contingent Consideration, Asset		(235)									(163)
Additional Paid in Capital																		$ 6,022																					$ 1,013
Derivative Asset, Noncurrent | Successor [Member]																																$ 0
Derivative Asset, Noncurrent		$ 669									$ 630

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