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] 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)	1,519								485					304					317			273			418			227			91			106
Acquisition of CENG noncontrolling interest	0								0
Other comprehensive income (loss), net of income taxes	$ 90						90		(4)
Ending balance (in shares) at Sep. 30, 2020	977,405
Ending balance at Sep. 30, 2020	$ 35,103		19,362		(123)	16,749	(3,104)	2,219
Ending Balance at Sep. 30, 2020									14,924	3,114	(36)	2,213	9,633												10,069	(43)	10,112
Ending Balance at Sep. 30, 2020														11,095	1,588	8,060	(1,700)	3,147	4,488	3,014	1,474	4,054	2,191	1,863				3,222	2,058	1,164	1,684	1,089	595	1,388	1,271	117
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
Net income (loss)	$ 569					501		68	117	49		68		196			196		138		138	53		53	216	216		118		118	27		27	75		75
Appropriation of retained earnings for future dividends														0			(196)	196
Long -Term Incentive Plan Activity (shares)	68
Long-Term Incentive Plan Activity	$ 10		10
Employee stock purchase plan issuances (shares)	1,000
Employee stock purchase plan issuances	$ 16		16
Changes in equity of noncontrolling interests	(17)							(17)	(18)			(18)
Common stock dividends	(374)					(374)								(124)				(124)	(85)		(85)	(62)		(62)				(73)		(73)	(33)		(33)	(76)		(76)
Distributions to member									(469)	(469)															(183)	(183)
Contributions from parent									64				64	239		239			17	17		258	258		135		135	125	125		6	6		1	1
Other comprehensive income (loss), net of income taxes	$ 28						28	0	3	0	3	0
Ending balance (in shares) at Sep. 30, 2020	977,405
Ending balance at Sep. 30, 2020	$ 35,103		19,362		(123)	16,749	(3,104)	2,219
Ending Balance at Sep. 30, 2020									14,924	3,114	(36)	2,213	9,633												10,069	(43)	10,112
Ending Balance at Sep. 30, 2020														11,095	1,588	8,060	(1,700)	3,147	4,488	3,014	1,474	4,054	2,191	1,863				3,222	2,058	1,164	1,684	1,089	595	1,388	1,271	117
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)	1,441								(122)					609					383			290			535			264			135			141
Acquisition of CENG noncontrolling interest	885								885
Other comprehensive income (loss), net of income taxes	$ 177						177		(1)
Ending balance (in shares) at Sep. 30, 2021	980,150
Ending balance at Sep. 30, 2021	$ 34,259		20,271		(123)	16,926	(3,223)	408
Ending Balance at Sep. 30, 2021									12,035	1,185	(31)	401	10,480												10,641	(138)	10,779
Ending Balance at Sep. 30, 2021	$ 33,851													12,151	1,588	8,878	(1,639)	3,324	5,075	3,428	1,647	4,525	2,575	1,950				3,490	2,302	1,188	1,826	1,209	617	1,555	1,574	(19)
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														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
Net income (loss)	$ 1,229					1,203		26	633	607		26		220			220		111		111	36		36	266	266		130		130	50		50	90		90
Appropriation of retained earnings for future dividends														0			(220)	220
Long -Term Incentive Plan Activity (shares)	94
Long-Term Incentive Plan Activity	$ 9		9
Employee stock purchase plan issuances (shares)	391
Employee stock purchase plan issuances	$ 18		18
Changes in equity of noncontrolling interests	(13)							(13)	(13)			(13)
Acquisition of CENG noncontrolling interest	(885)		1,080					(1,965)	(885)			(1,965)	1,080
Deferred Tax Liability Adjustment - Noncontrolling Interest	(290)		(290)						(288)				(288)
Common stock dividends	(375)					(375)								(127)				(127)	(85)		(85)	(73)		(73)				(98)		(98)	(43)		(43)	(51)		(51)
Distributions to member									(457)	(457)															(191)	(191)
Contributions from parent									64				64	198		198			19	19		257	257		107		107	106	106
Other comprehensive income (loss), net of income taxes	$ 66						66		(4)	0	(4)	0
Ending balance (in shares) at Sep. 30, 2021	980,150
Ending balance at Sep. 30, 2021	$ 34,259		$ 20,271		$ (123)	$ 16,926	$ (3,223)	$ 408
Ending Balance at Sep. 30, 2021									$ 12,035	$ 1,185	$ (31)	$ 401	$ 10,480												$ 10,641	$ (138)	$ 10,779
Ending Balance at Sep. 30, 2021	$ 33,851													12,151	$ 1,588	$ 8,878	$ (1,639)	$ 3,324	$ 5,075	$ 3,428	$ 1,647	$ 4,525	$ 2,575	$ 1,950				$ 3,490	$ 2,302	$ 1,188	$ 1,826	$ 1,209	$ 617	$ 1,555	$ 1,574	$ (19)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Appropriation of retained earnings for future dividends														$ 3,324