Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Debt and Credit Agreements - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 25
Commercial Paper [Member]
Line of Credit Facility [Line Items]
Commercial Paper	870	$ 89
Line of credit facility, maximum borrowing capacity	9,000	$ 9,000
Commercial Paper [Member] | Exelon Corporate [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	600
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	10,559
Line of Credit Facility, Capacity Available for Trade Purchases	7,353
Revolving Credit Facility [Member] | 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	458
Corporate, Non-Segment [Member] | Exelon Corporate [Member]
Line of Credit Facility [Line Items]
Short-term Bank Loans and Notes Payable	$ 500
London Interbank Offered Rate (LIBOR) [Member] | Corporate, Non-Segment [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate Terms	0.95%
Exelon Corporate [Member] | Commercial Paper [Member]
Line of Credit Facility [Line Items]
Commercial Paper	$ 136