Related Party Transactions - Current Receivables From/Payables To Affiliates (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 234	$ 523
Accounts Payable, Related Parties, Current	6	5
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	66	121
Accounts Receivable, Related Parties, Current	3	16
Commonwealth Edison Co [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		13
Commonwealth Edison Co [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	66	121
Commonwealth Edison Co [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	3	3
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	38	70
Accounts Receivable, Related Parties, Current	0	1
PECO Energy Co [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		0
PECO Energy Co [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
PECO Energy Co [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	37	48
Accounts Receivable, Related Parties, Current	0	1
Baltimore Gas and Electric Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		0
Baltimore Gas and Electric Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
Baltimore Gas and Electric Company [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Pepco Holdings LLC [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	51	104
Accounts Receivable, Related Parties, Current	0	2
Pepco Holdings LLC [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	18	16
Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	34	59
Accounts Receivable, Related Parties, Current	0	0
Potomac Electric Power Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		0
Potomac Electric Power Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Potomac Electric Power Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	15	33
Accounts Receivable, Related Parties, Current	0	1
Delmarva Power and Light Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		0
Delmarva Power and Light Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
Delmarva Power and Light Company [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	23	31
Accounts Receivable, Related Parties, Current	0	2
Atlantic City Electric Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		0
Atlantic City Electric Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
Atlantic City Electric Company [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
Atlantic City Electric Company [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Business Services Company [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	173	306
Business Services Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		102
Business Services Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	64	71
Business Services Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	33	36
Business Services Company [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	35	41
Business Services Company [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	7	5
Business Services Company [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	19	21
Business Services Company [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	3	17
Business Services Company [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	12	13
Business Services Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	39	32
PHI Service Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		0
PHI Service Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	0
PHI Service Company [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	15	12
PHI Service Company [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	12	11
PHI Service Company [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	11	9
PHI Service Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Other Legal Entities [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	3	14
Accounts Receivable, Related Parties, Current	19	47
Other Legal Entities [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		16
Other Legal Entities [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	2	9
Other Legal Entities [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	5	4
Other Legal Entities [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	2	3
Other Legal Entities [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	10	9
Other Legal Entities [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	3
Other Legal Entities [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
Other Legal Entities [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 0	2
Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		131
Accounts Receivable, Related Parties, Current		117
Exelon Generation Co LLC Affiliate [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		41
Exelon Generation Co LLC Affiliate [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		30
Exelon Generation Co LLC Affiliate [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		4
Exelon Generation Co LLC Affiliate [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		0
Exelon Generation Co LLC Affiliate [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		20
Exelon Generation Co LLC Affiliate [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		4
Exelon Generation Co LLC Affiliate [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		7
Exelon Generation Co LLC Affiliate [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current		$ 11