Asset Impairments - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) MW	Sep. 30, 2018 USD ($)
Property, Plant and Equipment [Line Items]
Net Income (Loss) Attributable to Noncontrolling Interest	$ (12)	$ 67	$ 56	$ 121
Deferred Income Taxes and Tax Credits			412	97
Impairment of long-lived assets			174	49
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Net Income (Loss) Attributable to Noncontrolling Interest	(13)	$ 66	56	120
Deferred Income Taxes and Tax Credits			201	(278)
Impairment of long-lived assets			174	$ 49
Antelope Valley [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	730		730
Impairment of long-lived assets			$ 0
Antelope Valley [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Capacity Of Facility Of Company Owned Solar Distribution Generation Facilities | MW			242
Long-lived assets	730		$ 730
Impairment of long-lived assets			0
ExGen Renewables IV, LLC [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	1,930		1,930
ExGen Renewables IV, LLC [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	1,930		$ 1,930
Certain Distributed Energy Companies [Member]
Property, Plant and Equipment [Line Items]
Equity Method Investment, Other than Temporary Impairment	164
Net Income (Loss) Attributable to Noncontrolling Interest	96
Deferred Income Taxes and Tax Credits	(46)
Income (Loss) from Equity Method Investments	(15)
Certain Distributed Energy Companies [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Equity Method Investment, Other than Temporary Impairment	164
Net Income (Loss) Attributable to Noncontrolling Interest	96
Deferred Income Taxes and Tax Credits	(46)
Income (Loss) from Equity Method Investments	$ (15)