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	1,288	938	210	183	938						1,288	210							183
Long-term incentive plan activity						846
Appropriation of retained earnings for future dividends				0															(183)	183
Long-term incentive plan activity	48					48			0		0
Common stock dividends	(698)		(184)	(150)							(698)	(184)								(150)
Distribution to members		0			0
Allocation of tax benefit from member		0								0
Allocation of tax benefit from parent			0				0
Preferred security dividends			(2)									(2)
Repayment of receivable from parent			0
Other comprehensive income (loss), net of tax	(86)	(323)	0	0									(86)	(323)
Ending Balance at Jun. 30, 2011	14,112		2,907	6,943			2,361	1,588				546			(1)			4,992	(1,639)	2,003
Ending Balance at Jun. 30, 2011	14,115					9,054			(2,327)		9,894		(2,509)			3
Ending Balance at Jun. 30, 2011						697,435
Ending Balance at Jun. 30, 2011		7,792			3,571					3,526				690			5
Beginning Balance at Mar. 31, 2011
Net income	620	443	83	114
Other comprehensive income (loss), net of tax	(111)	(254)	0	0
Ending Balance at Jun. 30, 2011	14,112		2,907	6,943				1,588							(1)			4,992
Ending Balance at Jun. 30, 2011	14,115															3
Ending Balance at Jun. 30, 2011		$ 7,792															$ 5