Consolidated Statement of Changes in Shareholders Equity (Unaudited) (USD $) In Millions, except Share data in Thousands	Total	Exelon Generation Co L L C [Member]	PECO Energy Co [Member]	Commonwealth Edison Co [Member]	Undistributed Earnings [Member] Exelon Generation Co L L C [Member]	Common Stock	Common Stock PECO Energy Co [Member]	Common Stock Commonwealth Edison Co [Member]	Treasury Stock	Membership Interest [Member] Exelon Generation Co L L C [Member]	Retained Earnings	Retained Earnings PECO Energy Co [Member]	Accumulated Other Comprehensive (Loss) Income, Net	Accumulated Other Comprehensive (Loss) Income, Net Exelon Generation Co L L C [Member]	Accumulated Other Comprehensive (Loss) Income, Net Commonwealth Edison Co [Member]	Noncontrolling Interest	Noncontrolling Interest Exelon Generation Co L L C [Member]	Other Paid-In Capital Commonwealth Edison Co [Member]	Retained Deficit Unappropriated Commonwealth Edison Co [Member]	Retained Earnings Appropriated Commonwealth Edison Co [Member]
Beginning Balance at Dec. 31, 2010	$ 13,560		$ 2,883	$ 6,910			$ 2,361	$ 1,588				$ 522			$ (1)			$ 4,992	$ (1,639)	$ 1,970
Beginning Balance at Dec. 31, 2010	13,563					9,006			(2,327)		9,304		(2,423)			3
Beginning Balance at Dec. 31, 2010						696,589
Beginning Balance at Dec. 31, 2010		7,177			2,633					3,526				1,013			5
Net income	1,889	1,325	314	295	1,325						1,889	314							295
Long-term incentive plan activity						1,167
Appropriation of retained earnings for future dividends				0															(295)	295
Long-term incentive plan activity	71					71			0		0
Common stock dividends	(1,047)		(268)	(225)							(1,047)	(268)								(225)
Distribution to members		(61)			(61)
Allocation of tax benefit from member		30								30
Allocation of tax benefit from parent			18				18
Preferred security dividends			(3)									(3)
Other comprehensive income (loss), net of tax	(117)	(448)	0	0									(117)	(448)
Ending Balance at Sep. 30, 2011	14,356		2,944	6,980			2,379	1,588				565			(1)			4,992	(1,639)	2,040
Ending Balance at Sep. 30, 2011	14,359					9,077			(2,327)		10,146		(2,540)			3
Ending Balance at Sep. 30, 2011						697,756
Ending Balance at Sep. 30, 2011		8,023			3,897					3,556				565			5
Beginning Balance at Jun. 30, 2011
Net income	601	386	105	112
Other comprehensive income (loss), net of tax	(31)	(125)	0	0
Ending Balance at Sep. 30, 2011	14,356		2,944	6,980				1,588							(1)			4,992
Ending Balance at Sep. 30, 2011	14,359															3
Ending Balance at Sep. 30, 2011		$ 8,023															$ 5