Accounts Receivable - Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	$ (160)	$ (150)	$ (120)
Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(47)	(32)	(33)
PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(39)	(42)	(31)
Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(17)	(15)	(8)
Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(24)	(43)	(17)
Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(9)	(24)	(7)
Delmarva Power & Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(5)	(16)	(4)
Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(10)	(2)	(5)
Customer accounts receivable
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	366	243
Current Period Provision for Expected Credit Losses	126	248
Writeoffs, net of recoveries	117	69
Allowance change due to sale of customer accounts		56
Ending balance	375	366	243
Customer accounts receivable | Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	97	59
Current Period Provision for Expected Credit Losses	21	62
Writeoffs, net of recoveries	45	24
Allowance change due to sale of customer accounts		0
Ending balance	73	97	59
Customer accounts receivable | PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	116	55
Current Period Provision for Expected Credit Losses	23	79
Writeoffs, net of recoveries	34	18
Allowance change due to sale of customer accounts		0
Ending balance	105	116	55
Customer accounts receivable | Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	35	12
Current Period Provision for Expected Credit Losses	15	30
Writeoffs, net of recoveries	12	7
Allowance change due to sale of customer accounts		0
Ending balance	38	35	12
Customer accounts receivable | Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	86	37
Current Period Provision for Expected Credit Losses	37	64
Writeoffs, net of recoveries	19	15
Allowance change due to sale of customer accounts		0
Ending balance	104	86	37
Customer accounts receivable | Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	32	13
Current Period Provision for Expected Credit Losses	13	24
Writeoffs, net of recoveries	8	5
Allowance change due to sale of customer accounts		0
Ending balance	37	32	13
Customer accounts receivable | Delmarva Power & Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	22	11
Current Period Provision for Expected Credit Losses	6	15
Writeoffs, net of recoveries	10	4
Allowance change due to sale of customer accounts		0
Ending balance	18	22	11
Customer accounts receivable | Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	32	13
Current Period Provision for Expected Credit Losses	18	25
Writeoffs, net of recoveries	1	6
Allowance change due to sale of customer accounts		0
Ending balance	49	32	13
Other Receivables
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	71	48
Current Period Provision for Expected Credit Losses	15	33
Writeoffs, net of recoveries	10	10
Ending balance	76	71	48
Other Receivables | Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	21	20
Current Period Provision for Expected Credit Losses	(2)	5
Writeoffs, net of recoveries	2	4
Ending balance	17	21	20
Other Receivables | PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	8	7
Current Period Provision for Expected Credit Losses	3	3
Writeoffs, net of recoveries	4	2
Ending balance	7	8	7
Other Receivables | Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	9	5
Current Period Provision for Expected Credit Losses	4	7
Writeoffs, net of recoveries	4	3
Ending balance	9	9	5
Other Receivables | Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	33	16
Current Period Provision for Expected Credit Losses	6	18
Writeoffs, net of recoveries	0	1
Ending balance	39	33	16
Other Receivables | Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	13	7
Current Period Provision for Expected Credit Losses	3	6
Writeoffs, net of recoveries	0	0
Ending balance	16	13	7
Other Receivables | Delmarva Power & Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	9	4
Current Period Provision for Expected Credit Losses	(1)	5
Writeoffs, net of recoveries	0	0
Ending balance	8	9	4
Other Receivables | Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	11	5
Current Period Provision for Expected Credit Losses	4	7
Writeoffs, net of recoveries	0	1
Ending balance	$ 15	$ 11	$ 5