The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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Variable Interest Entities - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Apr. 01, 2014
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 74
Exelon Generation Co L L C [Member] \| Distributed Energy Company
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		90.00%
Exelon Generation Co L L C [Member] \| VIE Distributed Energy Company
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		90.00%
CENG [Member] \| Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		50.01%
EGRP [Member] \| Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		51.00%
Antelope Valley [Member] \| Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		100.00%
Distributed Energy Company \| Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		31.00%
NER \| Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		100.00%
Variable Interest Entity, Primary Beneficiary [Member] \| CENG [Member] \| Payment Guarantee [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 245
Variable Interest Entity, Primary Beneficiary [Member] \| CENG [Member] \| Financial Guarantee [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 165
Variable Interest Entity, Primary Beneficiary [Member] \| CENG [Member] \| Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		49.99%
Guarantor Obligations, Current Carrying Value	$ 688
Variable Interest Entity, Primary Beneficiary [Member] \| EGRP [Member] \| Exelon Generation Co L L C [Member] \| Wind project entities [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		100.00%
Variable Interest Entity, Primary Beneficiary [Member] \| EGRP [Member] \| Exelon Generation Co L L C [Member] \| Solar project entities [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		100.00%