Related Party Transactions - BSC and PHISCO Service Companies (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Exelon Business Services Co Affiliate
Related Party Transaction [Line Items]
Related party transaction capitalized costs support services	$ 117	$ 162	$ 251	$ 323
Exelon Business Services Co Affiliate \| Commonwealth Edison Co
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	109	100	212	200
Related party transaction capitalized costs support services	51	61	111	124
Exelon Business Services Co Affiliate \| PECO Energy Co
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	68	61	133	120
Related party transaction capitalized costs support services	19	28	40	54
Exelon Business Services Co Affiliate \| Baltimore Gas and Electric Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	71	63	137	125
Related party transaction capitalized costs support services	20	32	41	65
Exelon Business Services Co Affiliate \| Pepco Holdings LLC
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	58	49	116	100
Related party transaction capitalized costs support services	28	41	58	80
Exelon Business Services Co Affiliate \| Potomac Electric Power Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	37	32	72	63
Related party transaction capitalized costs support services	12	17	25	34
Exelon Business Services Co Affiliate \| Delmarva Power and Light Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	23	20	45	40
Related party transaction capitalized costs support services	9	12	18	24
Exelon Business Services Co Affiliate \| Atlantic City Electric Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	19	16	36	32
Related party transaction capitalized costs support services	6	9	13	18
PHI Service Co Affiliate
Related Party Transaction [Line Items]
Related party transaction capitalized costs support services	28	29	51	53
PHI Service Co Affiliate \| Pepco Holdings LLC
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	0	0	0	0
Related party transaction capitalized costs support services	28	29	51	53
PHI Service Co Affiliate \| Potomac Electric Power Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	35	32	67	62
Related party transaction capitalized costs support services	12	12	22	23
PHI Service Co Affiliate \| Delmarva Power and Light Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	27	26	51	50
Related party transaction capitalized costs support services	8	9	15	16
PHI Service Co Affiliate \| Atlantic City Electric Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	25	24	51	47
Related party transaction capitalized costs support services	$ 7	$ 8	$ 14	$ 14