Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Debt and Credit Agreements - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Commercial Paper
Line of Credit Facility [Line Items]
Commercial Paper	$ 1,031	$ 870
Line of credit facility, maximum borrowing capacity	9,000	9,000
Commercial Paper | Exelon Corporate [Member]
Line of Credit Facility [Line Items]
Commercial Paper	0	$ 136
Line of credit facility, maximum borrowing capacity	600
Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	10,644
Line of Credit Facility, Capacity Available for Trade Purchases	7,698
Revolving Credit Facility | Exelon Corporate [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	600
Line of Credit Facility, Capacity Available for Trade Purchases	594
Corporate, Non-Segment [Member] | Exelon Corporate [Member]
Line of Credit Facility [Line Items]
Short-Term Loan Agreements	500
Corporate, Non-Segment [Member] | Revolving Credit Facility | Exelon Corporate [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 550
London Interbank Offered Rate (LIBOR) [Member] | Corporate, Non-Segment [Member]
Line of Credit Facility [Line Items]
Debt instrument, interest rate, stated percentage	0.65%	0.95%
London Interbank Offered Rate (LIBOR) [Member] | Corporate, Non-Segment [Member] | Line of credit
Line of Credit Facility [Line Items]
Debt instrument, interest rate, stated percentage	1.75%
Exelon Corporate [Member] | Corporate, Non-Segment [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 550