Accounts Receivable - Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses	$ (78)	$ (85)
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses	(17)	(13)
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses	(27)	(24)
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses	(18)	(4)
Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses	(18)	(10)
Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses	(9)	(5)
Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses	(6)	(4)
Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current period provision for expected credit losses	(3)	(1)
Customer accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	320	334
Current period provision for expected credit losses	110	70
Writeoffs, net of recoveries	41	27
Ending balance	389	377
Customer accounts receivable | Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	73	97
Current period provision for expected credit losses	26	21
Writeoffs, net of recoveries	7	15
Ending balance	92	103
Customer accounts receivable | PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	105	116
Current period provision for expected credit losses	31	20
Writeoffs, net of recoveries	11	6
Ending balance	125	130
Customer accounts receivable | Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	38	35
Current period provision for expected credit losses	26	9
Writeoffs, net of recoveries	5	1
Ending balance	59	43
Customer accounts receivable | Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	104	86
Current period provision for expected credit losses	27	20
Writeoffs, net of recoveries	18	5
Ending balance	113	101
Customer accounts receivable | Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	37	32
Current period provision for expected credit losses	11	11
Writeoffs, net of recoveries	8	2
Ending balance	40	41
Customer accounts receivable | Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	18	22
Current period provision for expected credit losses	7	6
Writeoffs, net of recoveries	1	3
Ending balance	24	25
Customer accounts receivable | Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	49	32
Current period provision for expected credit losses	9	3
Writeoffs, net of recoveries	9	0
Ending balance	49	35
Other receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	72	71
Current period provision for expected credit losses	14	10
Writeoffs, net of recoveries	5	2
Ending balance	81	79
Other receivables | Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	17	21
Current period provision for expected credit losses	4	1
Writeoffs, net of recoveries	1	0
Ending balance	20	22
Other receivables | PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	7	8
Current period provision for expected credit losses	3	4
Writeoffs, net of recoveries	1	1
Ending balance	9	11
Other receivables | Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	9	9
Current period provision for expected credit losses	3	1
Writeoffs, net of recoveries	1	1
Ending balance	11	9
Other receivables | Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	39	33
Current period provision for expected credit losses	4	4
Writeoffs, net of recoveries	2	0
Ending balance	41	37
Other receivables | Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	16	13
Current period provision for expected credit losses	2	2
Writeoffs, net of recoveries	0	0
Ending balance	18	15
Other receivables | Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	8	9
Current period provision for expected credit losses	1	1
Writeoffs, net of recoveries	0	0
Ending balance	9	10
Other receivables | Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	15	11
Current period provision for expected credit losses	1	1
Writeoffs, net of recoveries	2	0
Ending balance	$ 14	$ 12