Asset Impairments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Asset Held-for-use					$ 552	$ 591	$ 201
Net income (loss) attributable to noncontrolling interests					123	(9)	92
Deferred Income Taxes and Tax Credits					$ 18	$ 309	$ 681
Certain Distributed Energy Companies [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Net income (loss) attributable to noncontrolling interests				$ 96
Equity Method Investment, Other than Temporary Impairment				164
Deferred Income Taxes and Tax Credits				(46)
Income (Loss) from Equity Method Investments				$ (15)
Generation New England [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Asset Held-for-use		$ 350	$ 500
Contracted Wind Project | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Asset Held-for-use	$ 45
Net income (loss) attributable to noncontrolling interests	$ 21