Related Party Transactions - BSC and PHISCO Service Companies (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Exelon Business Services Co Affiliate
Related Party Transaction [Line Items]
Related party transaction capitalized costs support services	$ 132	$ 156	$ 383	$ 478
Exelon Business Services Co Affiliate \| Commonwealth Edison Co
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	104	95	316	296
Related party transaction capitalized costs support services	54	63	166	186
Exelon Business Services Co Affiliate \| PECO Energy Co
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	55	58	188	178
Related party transaction capitalized costs support services	28	24	69	79
Exelon Business Services Co Affiliate \| Baltimore Gas and Electric Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	56	60	193	185
Related party transaction capitalized costs support services	21	28	62	92
Exelon Business Services Co Affiliate \| Pepco Holdings LLC
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	38	44	154	144
Related party transaction capitalized costs support services	29	41	87	121
Exelon Business Services Co Affiliate \| Potomac Electric Power Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	32	30	104	93
Related party transaction capitalized costs support services	10	18	35	52
Exelon Business Services Co Affiliate \| Delmarva Power and Light Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	20	19	65	58
Related party transaction capitalized costs support services	9	12	27	36
Exelon Business Services Co Affiliate \| Atlantic City Electric Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	16	15	52	47
Related party transaction capitalized costs support services	10	10	23	28
PHI Service Co Affiliate
Related Party Transaction [Line Items]
Related party transaction capitalized costs support services	19	29	71	83
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	19	29	71	83
PHI Service Co Affiliate \| Potomac Electric Power Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	27	29	94	91
Related party transaction capitalized costs support services	5	14	27	36
PHI Service Co Affiliate \| Delmarva Power and Light Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	22	24	73	75
Related party transaction capitalized costs support services	8	8	23	25
PHI Service Co Affiliate \| Atlantic City Electric Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	16	22	67	69
Related party transaction capitalized costs support services	$ 7	$ 7	$ 21	$ 22