Mergers, Acquisitions, and Dispositions - Assets Disposition Table (Details) - USD ($) $ in Millions	Jan. 21, 2015	Jun. 30, 2015	Dec. 31, 2014
Assets Disposition Table [Line Items]
Total assets held for sale		$ 1	$ 147
Accrued expenses		1,366	1,539
Other current liabilities		941	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		1	147
Accrued expenses		732	886
Other current liabilities		$ 453	$ 605
Proceed from sale of asset net of tax	$ 1,400