Early Nuclear Plant Retirements Early Nuclear Plant Retirements - Narrative (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Facility Closing [Member]
Property, Plant and Equipment [Line Items]
Other Expenses		$ 714
Facility Closing [Member] | Three Mile Island [Member]
Property, Plant and Equipment [Line Items]
Restructuring Reserve, Accrual Adjustment	$ 71
Other Expenses	$ 37
Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	42.59%