Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Related Party Transactions - Summary of Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Payables to affiliates, current	$ 5	$ 5
Exelon Corporate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	10	9	$ 9
Interest income from affiliates, net	30	39	42
Equity in earnings (losses) of unconsolidated affiliates	2,313	3,254	2,183
Contributions from member	3,372	2,514	2,302
Accounts receivable from affiliates, current	11	41
Note receivable from affiliates, current	598	679
Investments in affiliates	43,149	42,245
Notes receivable from affiliates, noncurrent	324	329
Payables to affiliates, current	457	363
Exelon Corporate [Member] \| Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	10	9	11
Interest income from affiliates, net	1	3	4
Accounts receivable from affiliates, current	0	11
Note receivable from affiliates, current	252	109
Investments in affiliates	196	197
Payables to affiliates, current	91	0
Exelon Corporate [Member] \| Other Affiliate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	0	0	(2)
Equity in earnings (losses) of unconsolidated affiliates	1	3	0
Investments in affiliates	(3)	(4)
Exelon Corporate [Member] \| Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Interest income from affiliates, net	29	36	36
Equity in earnings (losses) of unconsolidated affiliates	589	1,125	369
Accounts receivable from affiliates, current	3	13
Note receivable from affiliates, current	285	558
Investments in affiliates	12,400	13,484
Notes receivable from affiliates, noncurrent	324	329
Payables to affiliates, current	2	0
Exelon Corporate [Member] \| Exelon Energy Delivery Company LLC [Member]
Related Party Transaction [Line Items]
Interest income from affiliates, net	0	0	2
Equity in earnings (losses) of unconsolidated affiliates	1,729	2,054	1,830
Investments in affiliates	30,103	28,147
Payables to affiliates, current	4	0
Exelon Corporate [Member] \| UII LLC [Member]
Related Party Transaction [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	0	97	0
Investments in affiliates	365	365
Payables to affiliates, current	360	360
Exelon Corporate [Member] \| Potomac Capital Investment Affiliate [Member]
Related Party Transaction [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	0	1	(17)
Investments in affiliates	62	62
Exelon Corporate [Member] \| Exelon Enterprise [Member]
Related Party Transaction [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	0	(16)	0
Accounts receivable from affiliates, current	1	0
Investments in affiliates	3	6
Payables to affiliates, current	0	3
Exelon Corporate [Member] \| Exelon INQB8R, LLC [Member] [Member]
Related Party Transaction [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	(6)	(8)	0
Investments in affiliates	23	(8)
Exelon Corporate [Member] \| Exelon Transmission Company LLC [Member]
Related Party Transaction [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	0	(2)	$ 1
Exelon Corporate [Member] \| Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates, current	0	2
Exelon Corporate [Member] \| PECO Energy Co [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates, current	1	2
Note receivable from affiliates, current	40	0
Exelon Corporate [Member] \| Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates, current	0	1
Exelon Corporate [Member] \| PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates, current	6	7
Exelon Corporate [Member] \| Exelon VTI, LLC [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates, current	0	5
Exelon Corporate [Member] \| Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Note receivable from affiliates, current	21	12
Exelon Corporate [Member] \| VEBA [Member]
Related Party Transaction [Line Items]
Investments in affiliates	$ 0	$ (4)

Amount for accounts payable to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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