Consolidated Statements of Changes in Shareholders Equity (Unaudited) - USD ($) shares in Thousands, $ in Millions	Total	Correcting Adjustment [Member]	Common Stock [Member]	Common Stock [Member] Correcting Adjustment [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] Retained 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 [Member]	Commonwealth Edison Co [Member] Other Paid-in-Capital [Member]	Commonwealth Edison Co [Member] Retained Earnings, Unappropriated [Member]	Commonwealth Edison Co [Member] Retained Earnings, Appropriated	PECO Energy Co [Member]	PECO Energy Co [Member] Common Stock [Member]	PECO Energy Co [Member] Retained Earnings [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] Retained Earnings [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]
Beginning balance (in shares) at Dec. 31, 2019	974,416
Beginning balance at Dec. 31, 2019	$ 34,573		$ 19,274		$ (123)	$ 16,267	$ (3,194)	$ 2,349
Beginning Balance at Dec. 31, 2019									$ 15,830	$ 3,950	$ (32)	$ 2,346	$ 9,566													$ 9,608	$ (10)	$ 9,618
Beginning Balance at Dec. 31, 2019														$ 10,677	$ 1,588		$ 7,572	$ (1,639)	$ 3,156	$ 4,178	$ 2,766	$ 1,412	$ 3,683	$ 1,907	$ 1,776				$ 2,907	$ 1,796	$ 1,111	$ 1,580	$ 977	$ 603	$ 1,276	$ 1,154	$ 122
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 376					582		(206)	(161)	45		(206)		168				168		140		140	181		181	108	108		52		52	45		45	13		13
Appropriation of retained earnings for future dividends																$ 0		(168)	168
Long -Term Incentive Plan Activity (shares)	1,354
Long-Term Incentive Plan Activity		$ (4)		$ (4)
Employee stock purchase plan issuances (shares)	470
Employee stock purchase plan issuances	$ 31		31
Changes in equity of noncontrolling interests	(9)							(9)	(11)			(11)
Sale of noncontrolling interests	2		2						2				2
Common stock dividends	(374)					(374)								(125)					(125)	(85)		(85)	(62)		(62)				(28)		(28)	(52)		(52)	(23)		(23)
Distributions to member									(468)	(468)																(134)	(134)
Contributions from parent														125			125			231	231					144		144	137	137		6	6		1	1
Other comprehensive income (loss), net of income taxes	$ 21						21		(9)	0	(9)	0
Ending balance (in shares) at Mar. 31, 2020	976,240
Ending balance at Mar. 31, 2020	$ 34,616		19,303		(123)	16,475	(3,173)	2,134
Ending Balance at Mar. 31, 2020									15,183	3,527	(41)	2,129	9,568													9,726	(36)	9,762
Ending Balance at Mar. 31, 2020														10,845	1,588		7,697	(1,639)	3,199	4,464	2,997	1,467	3,802	1,907	1,895				3,068	1,933	1,135	1,579	983	596	1,267	1,155	112
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Beginning balance (in shares) at Dec. 31, 2019	974,416
Beginning balance at Dec. 31, 2019	$ 34,573		19,274		(123)	16,267	(3,194)	2,349
Beginning Balance at Dec. 31, 2019									15,830	3,950	(32)	2,346	9,566													9,608	(10)	9,618
Beginning Balance at Dec. 31, 2019														10,677	1,588		7,572	(1,639)	3,156	4,178	2,766	1,412	3,683	1,907	1,776				2,907	1,796	1,111	1,580	977	603	1,276	1,154	122
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	950								368					107						178			219			202			109			64			31
Other comprehensive income (loss), net of income taxes	$ 62						62		(7)
Ending balance (in shares) at Jun. 30, 2020	976,337
Ending balance at Jun. 30, 2020	$ 34,871		19,336		(123)	16,622	(3,132)	2,168
Ending Balance at Jun. 30, 2020									15,227	3,534	(39)	2,163	9,569													9,901	(76)	9,977
Ending Balance at Jun. 30, 2020														10,784	1,588		7,821	(1,700)	3,075	4,418	2,997	1,421	3,805	1,933	1,872				3,052	1,933	1,119	1,684	1,083	601	1,388	1,270	118
Beginning balance (in shares) at Mar. 31, 2020	976,240
Beginning balance at Mar. 31, 2020	$ 34,616		19,303		(123)	16,475	(3,173)	2,134
Beginning Balance at Mar. 31, 2020									15,183	3,527	(41)	2,129	9,568													9,726	(36)	9,762
Beginning Balance at Mar. 31, 2020														10,845	1,588		7,697	(1,639)	3,199	4,464	2,997	1,467	3,802	1,907	1,895				3,068	1,933	1,135	1,579	983	596	1,267	1,155	112
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 574					521		53	529	476		53		(61)				(61)		39		39	39		39	94	94		57		57	19		19	18		18
Long -Term Incentive Plan Activity (shares)	148
Long-Term Incentive Plan Activity	$ 17		17
Employee stock purchase plan issuances (shares)		(51)
Employee stock purchase plan issuances	15		15
Changes in equity of noncontrolling interests	(19)							(19)	(19)			(19)
Sale of noncontrolling interests	1		1						1				1
Common stock dividends	(374)					(374)								(124)					(124)	(85)		(85)	(62)		(62)				(73)		(73)	(14)		(14)	(12)		(12)
Distributions to member									(469)	(469)																(134)	(134)
Contributions from parent														124			124						26	26		215		215				100	100		115	115
Other comprehensive income (loss), net of income taxes	$ 41						41		2	0	2	0
Ending balance (in shares) at Jun. 30, 2020	976,337
Ending balance at Jun. 30, 2020	$ 34,871		19,336		(123)	16,622	(3,132)	2,168
Ending Balance at Jun. 30, 2020									15,227	3,534	(39)	2,163	9,569													9,901	(76)	9,977
Ending Balance at Jun. 30, 2020														10,784	1,588		7,821	(1,700)	3,075	4,418	2,997	1,421	3,805	1,933	1,872				3,052	1,933	1,119	1,684	1,083	601	1,388	1,270	118
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Appropriation of retained earnings for future dividends														3,095
Beginning balance (in shares) at Dec. 31, 2020	977,466
Beginning balance at Dec. 31, 2020	$ 34,868		19,373		(123)	16,735	(3,400)	2,283
Beginning Balance at Dec. 31, 2020									14,676	2,805	(30)	2,277	9,624													10,044	(68)	10,112
Beginning Balance at Dec. 31, 2020	32,585													11,329	1,588		8,285	(1,639)	3,095	4,533	3,014	1,519	4,197	2,318	1,879				3,203	2,058	1,145	1,676	1,089	587	1,391	1,271	120
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ (264)					(289)		25	(769)	(793)		24		197				197		167		167	209		209	128	128		59		59	56		56	14		14
Appropriation of retained earnings for future dividends																0		(197)	197
Long -Term Incentive Plan Activity (shares)	640
Long-Term Incentive Plan Activity	$ 5		5
Employee stock purchase plan issuances (shares)	902
Employee stock purchase plan issuances	$ 34		34
Changes in equity of noncontrolling interests	(10)							(10)	(10)			(10)
Common stock dividends	(374)					(374)								(127)					(127)	(85)		(85)	(74)		(74)				(28)		(28)	(40)		(40)	(14)		(14)
Distributions to member									(458)	(458)																(81)	(81)
Contributions from parent														198			198									560		560	138	138		120	120		303	303
Other comprehensive income (loss), net of income taxes	$ 54						54		1	0	1	0
Ending balance (in shares) at Mar. 31, 2021	979,008
Ending balance at Mar. 31, 2021	$ 34,313		19,412		(123)	16,072	(3,346)	2,298
Ending Balance at Mar. 31, 2021									13,440	1,554	(29)	2,291	9,624													10,651	(21)	10,672
Ending Balance at Mar. 31, 2021														11,597	1,588		8,483	(1,639)	3,165	4,615	3,014	1,601	4,332	2,318	2,014				3,372	2,196	1,176	1,812	1,209	603	1,694	1,574	120
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Beginning balance (in shares) at Dec. 31, 2020	977,466
Beginning balance at Dec. 31, 2020	$ 34,868		19,373		(123)	16,735	(3,400)	2,283
Beginning Balance at Dec. 31, 2020									14,676	2,805	(30)	2,277	9,624													10,044	(68)	10,112
Beginning Balance at Dec. 31, 2020	32,585													11,329	1,588		8,285	(1,639)	3,095	4,533	3,014	1,519	4,197	2,318	1,879				3,203	2,058	1,145	1,676	1,089	587	1,391	1,271	120
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	211								(756)					390						271			254			269			134			86			51
Other comprehensive income (loss), net of income taxes	$ 111						111		3
Ending balance (in shares) at Jun. 30, 2021	979,665
Ending balance at Jun. 30, 2021	$ 34,500		19,454		(123)	16,098	(3,289)	2,360
Ending Balance at Jun. 30, 2021									12,985	1,035	(27)	2,353	9,624													10,459	(213)	10,672
Ending Balance at Jun. 30, 2021	$ 32,140													11,860	1,588		8,680	(1,639)	3,231	5,030	3,409	1,621	4,305	2,318	1,987				3,352	2,196	1,156	1,819	1,209	610	1,516	1,574	(58)
Beginning balance (in shares) at Mar. 31, 2021	979,008
Beginning balance at Mar. 31, 2021	$ 34,313		19,412		(123)	16,072	(3,346)	2,298
Beginning Balance at Mar. 31, 2021									13,440	1,554	(29)	2,291	9,624													10,651	(21)	10,672
Beginning Balance at Mar. 31, 2021														11,597	1,588		8,483	(1,639)	3,165	4,615	3,014	1,601	4,332	2,318	2,014				3,372	2,196	1,176	1,812	1,209	603	1,694	1,574	120
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 476					401		75	13	(61)		74		192				192		104		104	45		45	141	141		75		75	30		30	37		37
Appropriation of retained earnings for future dividends																$ 0		(192)	192
Long -Term Incentive Plan Activity (shares)	237
Long-Term Incentive Plan Activity	$ 24		24
Employee stock purchase plan issuances (shares)	420
Employee stock purchase plan issuances	$ 18		18
Changes in equity of noncontrolling interests	(13)							(13)	(12)			(12)
Common stock dividends	(375)					(375)								(126)					(126)	(84)		(84)	(72)		(72)				(95)		(95)	(23)		(23)	(215)		(215)
Distributions to member									(458)	(458)																(333)	(333)
Contributions from parent														197			197			395	395
Other comprehensive income (loss), net of income taxes	$ 57						57		2	0	2	0
Ending balance (in shares) at Jun. 30, 2021	979,665
Ending balance at Jun. 30, 2021	$ 34,500		$ 19,454		$ (123)	$ 16,098	$ (3,289)	$ 2,360
Ending Balance at Jun. 30, 2021									$ 12,985	$ 1,035	$ (27)	$ 2,353	$ 9,624													$ 10,459	$ (213)	$ 10,672
Ending Balance at Jun. 30, 2021	$ 32,140													11,860	$ 1,588		$ 8,680	$ (1,639)	$ 3,231	$ 5,030	$ 3,409	$ 1,621	$ 4,305	$ 2,318	$ 1,987				$ 3,352	$ 2,196	$ 1,156	$ 1,819	$ 1,209	$ 610	$ 1,516	$ 1,574	$ (58)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Appropriation of retained earnings for future dividends														$ 3,231