Consolidated Statements of Operations and Comprehensive Income (Unaudited) (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Prior service costs		$ 1		$ 2
Actuarial loss reclassified to periodic cost, taxes	(33)	(28)	(97)	(82)
Transition obligation		1		2
Pension and non-pension postretirement benefit plan valuation adjustment, taxes	6	43	(44)	51
Change in unrealized gain (loss) on cash flow hedges, taxes	(35)	(57)	(109)	36
Change in unrealized gain (loss) on marketable securities, taxes				1
Change in unrealized gain (loss) on equity investments taxes	9	11	32	15
Deferred Compensation Unit Valuation Adjustment tax			6
Exelon Generation Co L L C [Member]
Change in unrealized gain (loss) on cash flow hedges, taxes	(36)	(113)	(209)	(122)
Change in unrealized gain (loss) on equity investments taxes	$ 9	$ 11	$ 32	$ 15