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	498					486			(1)	13	310		311			(1)	200		200		14			14		106			106
Net income on common stock	486																193									100
Long-term incentive plan activity			1,782
Appropriation of retained earnings for future dividends																								(14)	14
Long-term incentive plan activity	61		61		0	0
Common stock dividends	(719)					(719)											(166)		(166)		(110)				(110)
Common stock issuance - Constellation merger - Shares
Common stock issuance - Constellation merger - Value
Contribution from parent										0	0			0		0
Distribution to members											(474)		(474)
Allocation of tax benefit from members											0			0
Preferred stock redemption premium	6			6													(6)		(6)
Allocation of tax benefit from parent																					174		174
Consolidated VIE dividend to non-controlling interest	(63)								(63)		(63)					(63)
Preferred security dividends	(7)					0				(7)							(1)		(1)							(6)
Other comprehensive income (loss), net of tax	94	[1]									(238)	[1]			(238)
Ending Balance at Jun. 30, 2013	21,353																3,009	2,388	620	1	7,401	1,588	5,188	(1,639)	2,264	2,268	1,360	190	908
Ending Balance at Jun. 30, 2013	21,588		16,693		(2,327)	9,660		(2,673)	42	193																2,458
Ending Balance at Jun. 30, 2013			891,307
Ending Balance at Jun. 30, 2013											12,197		3,005	8,873	275	44
Beginning Balance at Mar. 31, 2013
Net income	497										328						78				96					25
Net income on common stock	490																72									22
Preferred stock redemption premium							(6)
Other comprehensive income (loss), net of tax											(134)
Ending Balance at Jun. 30, 2013	21,353																3,009	2,388		1	7,401	1,588				2,268	1,360	190
Ending Balance at Jun. 30, 2013	21,588							(2,673)																		2,458
Ending Balance at Jun. 30, 2013											$ 12,197

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