Revenue from Contracts with Customers - Contract Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	$ 151	$ 33	$ 27
Contract with Customer, Liability, Cumulative Catch-up Adjustment to Revenue, Modification of Contract	97	219	94
Contract with Customer, Liability, Revenue Recognized	(110)	(98)	(88)
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination	3	(3)
Ending Balance - Contract Liabilities	141	151	33
Pepco Holdings LLC [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	118	0	0
Contract with Customer, Liability, Cumulative Catch-up Adjustment to Revenue, Modification of Contract	0	122	0
Contract with Customer, Liability, Revenue Recognized	(9)	(4)	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination	0	0
Ending Balance - Contract Liabilities	109	118	0
Potomac Electric Power Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	94	0	0
Contract with Customer, Liability, Cumulative Catch-up Adjustment to Revenue, Modification of Contract	0	98	0
Contract with Customer, Liability, Revenue Recognized	(7)	(4)	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination	0	0
Ending Balance - Contract Liabilities	87	94	0
Delmarva Power & Light Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	12	0	0
Contract with Customer, Liability, Cumulative Catch-up Adjustment to Revenue, Modification of Contract	0	12	0
Contract with Customer, Liability, Revenue Recognized	(1)	0	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination	0	0
Ending Balance - Contract Liabilities	11	12	0
Atlantic City Electric Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	12	0	0
Contract with Customer, Liability, Cumulative Catch-up Adjustment to Revenue, Modification of Contract	0	12	0
Contract with Customer, Liability, Revenue Recognized	(1)	0	0
Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination	0	0
Ending Balance - Contract Liabilities	$ 11	$ 12	$ 0