Mergers, Acquisitions, and Dispositions - Changes in Ownership Equity (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Aug. 06, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Schedule of Changes in Ownership Interest [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic		$ 1,203	$ 501	$ 1,315	$ 1,604
Acquisition of CENG noncontrolling interest		(885)		885	0
Deferred Tax Liability Adjustment - Noncontrolling Interest		(290)
Change from net income (loss) attributable to ownership interest and transfers from Noncontrolling Interest		$ 1,993		$ 2,105
CENG [Member]
Schedule of Changes in Ownership Interest [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.99%	49.99%		49.99%		49.99%
Exelon Generation Co L L C [Member]
Schedule of Changes in Ownership Interest [Line Items]
Acquisition of CENG noncontrolling interest		$ (885)		$ 885	0
Deferred Tax Liability Adjustment - Noncontrolling Interest		(288)
Change from net income (loss) attributable to ownership interest and transfers from Noncontrolling Interest		1,399		545
Net Income (Loss) Attributable to Parent		$ 607	$ 49	$ (247)	$ 570
Exelon Generation Co L L C [Member] | CENG [Member]
Schedule of Changes in Ownership Interest [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.99%	49.99%		49.99%		49.99%
CENG [Member]
Schedule of Changes in Ownership Interest [Line Items]
Acquisition of CENG noncontrolling interest	$ 885	$ 1,080		$ 1,080
Deferred Tax Liability Adjustment - Noncontrolling Interest		(290)		(290)
CENG [Member] | Exelon Generation Co L L C [Member]
Schedule of Changes in Ownership Interest [Line Items]
Acquisition of CENG noncontrolling interest	$ 885	1,080		1,080
Deferred Tax Liability Adjustment - Noncontrolling Interest		$ (288)		$ (288)