Related Party Transactions - BSC and PHISCO Service Companies (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Exelon Business Services Co Affiliate
Related Party Transaction [Line Items]
Related party transaction capitalized costs support services	$ 141	$ 162	$ 458	$ 502
Exelon Business Services Co Affiliate \| Commonwealth Edison Co
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	102	92	306	263
Related party transaction capitalized costs support services	55	71	189	230
Exelon Business Services Co Affiliate \| PECO Energy Co
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	61	55	180	160
Related party transaction capitalized costs support services	23	29	81	89
Exelon Business Services Co Affiliate \| Baltimore Gas and Electric Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	61	58	182	166
Related party transaction capitalized costs support services	25	23	74	69
Exelon Business Services Co Affiliate \| Pepco Holdings LLC
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	46	50	145	135
Related party transaction capitalized costs support services	38	39	114	114
Exelon Business Services Co Affiliate \| Potomac Electric Power Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	29	30	92	85
Related party transaction capitalized costs support services	16	13	51	41
Exelon Business Services Co Affiliate \| Delmarva Power and Light Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	19	19	58	54
Related party transaction capitalized costs support services	11	12	36	32
Exelon Business Services Co Affiliate \| Atlantic City Electric Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	16	16	48	45
Related party transaction capitalized costs support services	9	13	24	39
PHI Service Co Affiliate
Related Party Transaction [Line Items]
Related party transaction capitalized costs support services	27	25	85	74
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	27	24	85	73
PHI Service Co Affiliate \| Potomac Electric Power Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	28	31	94	91
Related party transaction capitalized costs support services	12	9	36	30
PHI Service Co Affiliate \| Delmarva Power and Light Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	24	24	75	73
Related party transaction capitalized costs support services	8	7	25	22
PHI Service Co Affiliate \| Atlantic City Electric Company
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	23	23	71	67
Related party transaction capitalized costs support services	$ 7	$ 7	$ 24	$ 20