Related Party Transactions - Noncurrent Receivables from/Payables to affiliates (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Related Party Transaction [Line Items] | ||
| Accounts Payable, Related Parties, Noncurrent | $ 3,017 | $ 3,103 |
| Commonwealth Edison Co Affiliate [Member] | ||
| Related Party Transaction [Line Items] | ||
| Accounts Payable, Related Parties, Noncurrent | 2,541 | 2,622 |
| PECO Energy Co Affiliate [Member] | ||
| Related Party Transaction [Line Items] | ||
| Accounts Payable, Related Parties, Noncurrent | $ 475 | $ 480 |