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]	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]	Exelon Generation Co L L C [Member]		Exelon Generation Co L L C [Member] Undistributed Earnings [Member]	Exelon Generation Co L L C [Member] Membership Interest [Member]	Exelon Generation Co L L C [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Exelon Generation Co L L C [Member] Noncontrolling Interest [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] Membership Interest [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]	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]	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]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated other comprehensive loss, net	[1]	$ (2,684)								$ 1					$ (36)
Other Comprehensive Income (Loss), Net of Tax | Predecessor [Member]																									$ 1
Other Comprehensive Income (Loss), Net of Tax	[1]	11													(17)
Net income | Predecessor [Member]																									53
Net income		738								139					485						$ 109											$ 26			$ 32			$ 9			$ 90
Accumulated other comprehensive loss, net	[1]	(2,673)								1					(53)
Common Stock, Value, Issued | Predecessor [Member]																											$ 3
Common Stock, Value, Issued		18,676								2,455											1,367											1,122			612			773			1,588
Retained Earnings (Accumulated Deficit) | Predecessor [Member]																									617				$ 617
Retained Earnings (Accumulated Deficit)		12,068								780					2,701		$ 2,701				1,320														625			227			978
Accumulated other comprehensive loss, net | Predecessor [Member]																									(36)					$ (36)
Accumulated other comprehensive loss, net		(2,624)	[1]							1	[1]				(63)	[1]			$ (63)	$ 1,307
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest | Predecessor [Member]																									4,413
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																																1,118									5,677
Derivative Asset, Noncurrent		$ 758													733
Beginning Balance (in shares) at Dec. 31, 2015		954,668
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								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	8,243	$ 1,588	$ 5,677	$ (1,639)	$ 2,617
Beginning Balance (Predecessor [Member]) at Dec. 31, 2015																									3,832			$ 3,832
Beginning Balance at Dec. 31, 2015															8,997			$ 8,997
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax		28	[1]												(1)	[1]			(1)
Stock Issued During Period, Value, Employee Stock Purchase Plan		$ 9		9
Stock Issued During Period, Shares, Employee Stock Purchase Plans		351
Net income		$ 123				173		(53)	3	124			124		257		310		0	(53)	101		0	101								(108)		(108)	(72)		(72)	(100)		(100)	115			115
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared															55		55				(7)	(7)		0
Noncontrolling Interest, Increase from Sale of Parent Equity Interest															10
Long-term incentive plan activity (in shares)		1,783
Long-term incentive plan activity		$ 17		17
Employee stock purchase plan issuances (in shares)		351
Employee stock purchase plan issuances		$ 9		9
Appropriation of retained earnings for future dividends																																									0			(115)	115
Tax benefit on stock compensation		(16)		(16)
Common stock dividends		(287)				(287)			(3)	(69)			(69)								(45)		0	45											38		38	11		11	(91)				(91)
Contribution from parent															170			170			21	21		0																	39		39
Dividends																																(39)		(39)
Allocation of tax benefit from parent																																									1		1
Minority Interest Increase From Acquisition		2						2							2					2
Preferred security dividends		(3)																			(3)		0	(3)
Temporary Equity, Other Changes															19					(19)
Other comprehensive loss, net of income taxes of $53		28					28										0			0
Ending Balance at Mar. 31, 2016		$ 27,186		18,686	(2,327)	11,954	(2,596)	1,276	193												2,944											2,093
Ending Balance (in shares) at Mar. 31, 2016		956,802
Ending Balance at Mar. 31, 2016		$ 25,717								3,291		2,455	835	1							2,754	1,381	190	1,373								2,093	1,122	971	1,127	612	515	889	773	116	8,307	1,588	5,717	(1,639)	2,641
Beginning Balance (in shares) at Dec. 31, 2015		954,668
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								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	8,243	1,588	5,677	(1,639)	2,617
Beginning Balance (Predecessor [Member]) at Dec. 31, 2015																									3,832			$ 3,832
Beginning Balance at Dec. 31, 2015															8,997			$ 8,997
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]
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																									0
Net income | Successor [Member]																									(309)				(309)
Ending Balance at Mar. 31, 2016		$ 27,186		$ 18,686	$ (2,327)	$ 11,954	$ (2,596)	$ 1,276	$ 193												2,944											2,093
Ending Balance (in shares) at Mar. 31, 2016		956,802
Ending Balance at Mar. 31, 2016		$ 25,717								3,291		$ 2,455	$ 835	$ 1							2,754	$ 1,381	$ 190	$ 1,373								2,093	$ 1,122	$ 971	1,127	$ 612	$ 515	889	$ 773	$ 116	8,307	$ 1,588	$ 5,717	$ (1,639)	$ 2,641
Common Stock, Value, Issued | Predecessor [Member]																									3		$ 3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Additional Paid in Capital | Predecessor [Member]																										$ 3,835
Common Stock, Value, Issued		18,686								2,455											1,381											1,122			612			773			1,588
Retained Earnings (Accumulated Deficit) | Successor [Member]																									(309)				$ (309)
Retained Earnings (Accumulated Deficit)		11,954								835					2,956		$ 2,956				$ 1,373														$ 515			$ 116			1,002
Accumulated other comprehensive loss, net | Successor [Member]																									0					$ 0
Accumulated other comprehensive loss, net		(2,596)	[1]							$ 1	[1]				(64)	[1]			$ (64)	$ 1,275
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest | Successor [Member]																									6,672
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest															13,334
Business Combination, Contingent Consideration, Asset | Successor [Member]																									(235)
Business Combination, Contingent Consideration, Asset		235
Other Additional Capital | Successor [Member]																									(29)
Additional Paid in Capital																																$ 971									$ 5,717
Business Combination, Separately Recognized Transactions, Assets Recognized | Successor [Member]																									$ 45
Fresh-Start Adjustment, Increase (Decrease), Deferred Income Tax Liabilities, Noncurrent		59
Derivative Asset, Noncurrent		$ 841													$ 799

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