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] 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] Nonredeemable Preferred Stock [Member]	Baltimore Gas and Electric Company [Member] Retained Earnings [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]	Deferred Compensation, Share-based Payments [Member] Pepco Holdings LLC [Member]	Commitments [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]																														$ 4
Other Comprehensive Income (Loss), Net of Tax	[1]	58								(11)											0
Net income | Predecessor [Member]																														106
Net income		1,372								875						$ 189					209					$ 157											$ 68			$ 40			$ 15
Proceeds from Contributions from Parent | Predecessor [Member]																														0
Proceeds from Contributions from Parent																45										0											112			75			0
Payments to Acquire Businesses, Gross		(28)								(28)
Other Comprehensive Income (Loss), Net of Tax | Predecessor [Member]																														3
Other Comprehensive Income (Loss), Net of Tax		50								6
Net income | Predecessor [Member]																														53
Net income		633								390						99					70					47											42			8			6
Accumulated other comprehensive loss, net	[1]	(2,626)								(47)											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
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	$ 5,677	$ (1,639)	$ 2,617	3,236		$ 2,455	$ 780	$ 1	2,687	$ 1,367	$ 190	$ 1,320								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				1
Stock Issued During Period, Value, Employee Stock Purchase Plan | Predecessor [Member]																														3
Net income | Predecessor [Member]																														19			19
Employee stock purchase plan issuances | Predecessor [Member]																														3
Other comprehensive loss, net of income taxes of $53 | Predecessor [Member]																														1
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	5,677	(1,639)	2,617	3,236		2,455	780	1	2,687	1,367	190	1,320								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		59	[1]							(2)	[1]	0	(2)	0
Stock Issued During Period, Value, Employee Stock Purchase Plan		$ 17		17
Stock Issued During Period, Shares, Employee Stock Purchase Plans		599
Net income		$ 430				440		(17)	7	285		302	0	(17)		260			260		224			224		135		0	135								(60)		(60)	(60)		(60)	(97)		(97)	$ (262)
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared | Successor [Member]																														(16)
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared										111		111														(7)	(7)		0
Noncontrolling Interest, Increase from Sale of Parent Equity Interest										52
Long-term incentive plan activity (in shares)		2,349
Long-term incentive plan activity		$ 47		47
Employee stock purchase plan issuances (in shares)		599
Employee stock purchase plan issuances		$ 17		17
Appropriation of retained earnings for future dividends																0			(260)	260
Tax benefit on stock compensation		(18)		(18)
Common stock dividends		(582)				(582)			(7)							(183)				(183)	(139)			(139)		(90)		0	90											38		38	(11)		(11)
Contribution from parent										171					171	113		113								21	21		0								187	187		113	113		139	139
Dividends																																					(88)		(88)
Allocation of tax benefit from parent																5		5
Minority Interest Increase From Acquisition		2						2		2				2
Preferred security dividends		(7)																								(6)		0	(6)
Temporary Equity, Other Changes		(56)						(56)		56				(56)
Other comprehensive loss, net of income taxes of $53		59					59
Ending Balance at Jun. 30, 2016		$ 27,298		18,722	(2,327)	11,926	(2,565)	1,349	193																	2,930											2,279
Ending Balance (in shares) at Jun. 30, 2016		957,616
Ending Balance at Jun. 30, 2016		$ 25,756														8,438	1,588	5,795	(1,639)	2,694	3,321		2,455	865	1	2,740	1,381	190	1,359								2,279	1,309	970	1,252	725	527	1,031	912	119
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from Contributions from Parent																113										21											187			113			139
Payments to Acquire Businesses, Gross		(6,642)								(1)
Common Stock, Value, Issued | Predecessor [Member]																														3		$ 3
Additional Paid in Capital | Predecessor [Member]																															$ 3,835
Payments to Acquire Businesses, Gross | Successor [Member]																																															$ (29)	$ (33)
Beginning Balance (Predecessor [Member]) at Mar. 23, 2016																														4,439			636	(35)	3,838
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																														0
Net income | Successor [Member]																														(257)			(257)
Contribution from parent | Successor [Member]																														1,088
Ending Balance at Jun. 30, 2016		$ 27,298		18,722	(2,327)	11,926	(2,565)	1,349	193																	2,930											2,279
Ending Balance (in shares) at Jun. 30, 2016		957,616
Ending Balance at Jun. 30, 2016		$ 25,756														8,438	1,588	5,795	(1,639)	2,694	3,321		2,455	865	1	2,740	1,381	190	1,359								2,279	1,309	970	1,252	725	527	1,031	912	119
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from Contributions from Parent | Successor [Member]																														1,088
Payments to Acquire Businesses, Gross | Successor [Member]																																														(62)	$ (29)
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]																														235
Business Combination, Separately Recognized Transactions, Assets Recognized | Successor [Member]																														53
Fresh-Start Adjustment, Increase (Decrease), Deferred Income Tax Liabilities, Noncurrent | Successor [Member]																																				$ 59
Net income | Successor [Member]																																				$ 0
Ending Balance at Jun. 30, 2016		$ 27,298		18,722	(2,327)	11,926	(2,565)	1,349	193																	2,930											2,279
Ending Balance (in shares) at Jun. 30, 2016		957,616
Ending Balance at Jun. 30, 2016		$ 25,756														8,438	1,588	5,795	(1,639)	2,694	3,321		2,455	865	1	2,740	1,381	190	1,359								2,279	1,309	970	1,252	725	527	1,031	912	119
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																														0
Other Comprehensive Income (Loss), Net of Tax		31								0
Net income | Successor [Member]																														52
Net income		306								28						145					100					34											49			12			3			$ 52
Ending Balance at Jun. 30, 2016		$ 27,298		$ 18,722	$ (2,327)	$ 11,926	$ (2,565)	$ 1,349	$ 193																	2,930											2,279
Ending Balance (in shares) at Jun. 30, 2016		957,616
Ending Balance at Jun. 30, 2016		$ 25,756														8,438	$ 1,588	$ 5,795	$ (1,639)	$ 2,694	3,321		$ 2,455	$ 865	$ 1	2,740	$ 1,381	$ 190	$ 1,359								2,279	$ 1,309	$ 970	1,252	$ 725	$ 527	1,031	$ 912	$ 119
Common Stock, Value, Issued		18,722														1,588					2,455					1,381											1,309			725			912
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance | Successor [Member]																														8,028					$ 8,028
Beginning Balance										9,168					$ 9,168
Retained Earnings (Accumulated Deficit) | Successor [Member]																														(257)			$ (257)
Retained Earnings (Accumulated Deficit)		11,926								2,892		$ 2,892				1,055					865					$ 1,359														$ 527			$ 119
Accumulated other comprehensive loss, net | Successor [Member]																														0				$ 0
Accumulated other comprehensive loss, net		(2,565)	[1]							(65)	[1]		$ (65)	$ 1,348							$ 1	[1]
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest | Successor [Member]																														7,771
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest										13,343
Business Combination, Contingent Consideration, Asset | Successor [Member]																														(251)
Business Combination, Contingent Consideration, Asset		(235)								(163)
Additional Paid in Capital																$ 5,795																					$ 970
Derivative Asset, Noncurrent | Successor [Member]																														$ 0
Derivative Asset, Noncurrent		$ 546								$ 499

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