Consolidated Statement of Changes in Shareholders Equity (Unaudited) (USD $) In Millions, except Share data in Thousands	Total		Common Stock [Member]	Nonredeemable Preferred Stock [Member]	Treasury Stock	Retained Earnings	Retained Earnings Cumulative Preferred Stock [Member]	Accumulated Other Comprehensive (Loss) Income, Net	Noncontrolling Interest	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] Membership Interest [Member]	Exelon Generation Co L L C [Member] Accumulated Other Comprehensive (Loss) Income, Net	Exelon Generation Co L L C [Member] Noncontrolling Interest	PECO Energy Co [Member]	PECO Energy Co [Member] Common Stock [Member]	PECO Energy Co [Member] Retained Earnings	PECO Energy Co [Member] Accumulated Other Comprehensive (Loss) Income, Net	Commonwealth Edison Co [Member]	Commonwealth Edison Co [Member] Common Stock [Member]	Commonwealth Edison Co [Member] Other Paid-In Capital	Commonwealth Edison Co [Member] Retained Deficit Unappropriated	Commonwealth Edison Co [Member] Retained Earnings Appropriated	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
Beginning Balance at Dec. 31, 2012	$ 21,431																$ 2,982	$ 2,388	$ 593	$ 1	$ 7,323	$ 1,588	$ 5,014	$ (1,639)	$ 2,360	$ 2,168	$ 1,360	$ 190	$ 808
Beginning Balance at Dec. 31, 2012	21,730		16,632		(2,327)	9,893		(2,767)	106	193																2,358
Beginning Balance at Dec. 31, 2012			889,525
Beginning Balance at Dec. 31, 2012											12,665		3,168	8,876	513	108
Net income	1,235					1,224			(6)	17	795		801			(6)	292		292		140			140		160			160
Net income on common stock	1,224																285									150
Long-term incentive plan activity			2,122
Appropriation of retained earnings for future dividends																								(140)	140
Long-term incentive plan activity	84		84		0	0
Common stock dividends	(986)					(986)											(248)		(248)		(165)				(165)
Common stock issuance - Constellation merger - Shares
Common stock issuance - Constellation merger - Value
Contribution from parent										0	0			0		0
Distribution to members											(550)		(550)
Allocation of tax benefit from members											0			0
Preferred stock redemption premium	(6)			(6)													(6)		(6)
Allocation of tax benefit from parent																					175		175
Consolidated VIE dividend to non-controlling interest	(63)								(63)		(63)					(63)
Preferred security dividends	(11)					0				(11)							(1)		(1)							(10)		(10)
Other comprehensive income (loss), net of tax	106	[1]									(270)	[1]			(270)
Sale of noncontrolling interest											(3)			(3)
ImpairmentOfLongLivedAssetsToBeDisposedOf	(4)								(4)		(4)					(4)
Deconsolidation of VIE	(18)								(18)		(19)			(1)		(18)
Ending Balance at Sep. 30, 2013	21,859																3,019	2,388	630	1	7,473	1,588	5,189	(1,639)	2,335	2,318	1,360	190	958
Ending Balance at Sep. 30, 2013	22,067		16,716		(2,327)	10,131		(2,661)	15	193																2,508
Ending Balance at Sep. 30, 2013			891,647
Ending Balance at Sep. 30, 2013											12,551		3,419	8,872	243	17
Beginning Balance at Jun. 30, 2013
Net income	736										485						92				126					53
Net income on common stock	738																92									50
Preferred stock redemption premium							(6)
Other comprehensive income (loss), net of tax	12										(32)
Ending Balance at Sep. 30, 2013	21,859																3,019	2,388		1	7,473	1,588				2,318	1,360
Ending Balance at Sep. 30, 2013	22,067							(2,661)																		2,508
Ending Balance at Sep. 30, 2013											$ 12,551

[1] (a) All amounts are net of tax. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.