Related Party Transactions - BSC and PHISCO Service Companies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	$ 205	$ 114
PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	19	17
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	85	71
Commonwealth Edison Co [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	85	71
Related Party Transaction Capitalized Costs Support Services	85	45
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	51	41
PECO Energy Co [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	49	39
Related Party Transaction Capitalized Costs Support Services	36	17
Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	51	45
Baltimore Gas and Electric Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	51	43
Related Party Transaction Capitalized Costs Support Services	38	20
Pepco Holdings LLC [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	51	40
Pepco Holdings LLC [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	50	39
Related Party Transaction Capitalized Costs Support Services	46	32
Pepco Holdings LLC [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	19	17
Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	58	52
Potomac Electric Power Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	29	22
Related Party Transaction Capitalized Costs Support Services	17	13
Potomac Electric Power Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	29	30
Related Party Transaction Capitalized Costs Support Services	8	7
Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	42	39
Delmarva Power and Light Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	18	14
Related Party Transaction Capitalized Costs Support Services	14	10
Delmarva Power and Light Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	24	25
Related Party Transaction Capitalized Costs Support Services	6	5
Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	37	34
Atlantic City Electric Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	15	12
Related Party Transaction Capitalized Costs Support Services	15	8
Atlantic City Electric Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	21	22
Related Party Transaction Capitalized Costs Support Services	$ 5	$ 5