Subsequent Events - Narrative (Details) - USD ($)		3 Months Ended
	Feb. 15, 2021	Mar. 31, 2021	Feb. 22, 2021	Dec. 31, 2020
Subsequent Event [Line Items]
Debt Instrument, Collateral Amount				$ 2,200,000,000
Line of credit facility, remaining borrowing capacity				9,414,000,000
Subsequent Event [Member] | Texas-based generating assets
Subsequent Event [Line Items]
Debt Instrument, Collateral Amount			$ 1,400,000,000
Line of credit facility, remaining borrowing capacity			2,400,000,000
Subsequent Event [Member] | Maximum [Member] | Texas-based generating assets
Subsequent Event [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 9,000
Other Cost and Expense, Operating		$ 560,000,000
Subsequent Event [Member] | Minimum [Member] | Texas-based generating assets
Subsequent Event [Line Items]
Other Cost and Expense, Operating		710,000,000
Exelon Generation Co L L C [Member]
Subsequent Event [Line Items]
Debt Instrument, Collateral Amount				$ 2,200,000,000
Exelon Generation Co L L C [Member] | Subsequent Event [Member] | Texas-based generating assets
Subsequent Event [Line Items]
Debt Instrument, Collateral Amount			1,400,000,000
Line of credit facility, remaining borrowing capacity			$ 2,400,000,000
Exelon Generation Co L L C [Member] | Subsequent Event [Member] | Maximum [Member] | Texas-based generating assets
Subsequent Event [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 9,000
Other Cost and Expense, Operating		560,000,000
Exelon Generation Co L L C [Member] | Subsequent Event [Member] | Minimum [Member] | Texas-based generating assets
Subsequent Event [Line Items]
Other Cost and Expense, Operating		$ 710,000,000