Mergers, Acquisitions, and Dispositions - Assets Disposition Table (Details) - USD ($) $ in Millions		9 Months Ended
	Jan. 21, 2015	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014
Assets Disposition Table [Line Items]
Total assets held for sale			$ 4	$ 147
Accrued expenses			1,576	1,539
Other current liabilities			1,017	1,123
Exelon Generation Co L L C [Member]
Assets Disposition Table [Line Items]
Proceeds from Sale of Productive Assets	$ 1,800
Total assets held for sale			4	147
Accrued expenses			835	886
Other current liabilities			$ 546	$ 605
Asset Impairment Charges		$ 50
Proceed from sale of asset net of tax	$ 1,400