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Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

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Amount classified as assets attributable to disposal group held for sale or disposed of, expected to be disposed of within one year or the normal operating cycle, if longer.

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Amount of gain (loss) from deconsolidation of subsidiary and derecognition of group of assets constituting transfer of business or nonprofit activity, excluding conveyance of oil and gas mineral rights and transfer of good or service in contract with customer.

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The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Amount classified as liabilities attributable to disposal group held for sale or disposed of, expected to be disposed of within one year or the normal operating cycle, if longer.

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The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

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Mergers, Acquisitions and Dispositions - Dispositions Narrative (Details) $ in Millions			3 Months Ended			12 Months Ended
	Feb. 28, 2018 USD ($)	Nov. 07, 2017 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2019 USD ($) GW	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Dispositions [Line Items]
Disposal Group, Including Discontinued Operation, Assets, Current						$ 0	$ 904
Disposal Group, Including Discontinued Operation, Liabilities, Current						0	777
Asset Retirement Obligation, Revision of Estimate							20
Impairment of Long-Lived Assets Held-for-use						201	50	$ 573
Deconsolidation, Gain (Loss), Amount						0	0	213
Operating Expense [Member]
Business Dispositions [Line Items]
Asset Retirement Obligation, Revision of Estimate						(150)
ExGen Texas Power [Member]
Business Dispositions [Line Items]
Deconsolidation, Gain (Loss), Amount		$ 213
Oyster Creek [Member]
Business Dispositions [Line Items]
Disposal Group, Including Discontinued Operation, Assets, Current							897
Disposal Group, Including Discontinued Operation, Liabilities, Current							777
Oyster Creek [Member] \| Operating Expense [Member]
Business Dispositions [Line Items]
Asset Retirement Obligation, Revision of Estimate			$ 9	$ 84
Electrical Contracting Business [Member]
Business Dispositions [Line Items]
Proceeds from Divestiture of Businesses	$ 87
Exelon Generation Co L L C [Member]
Business Dispositions [Line Items]
Disposal Group, Including Discontinued Operation, Assets, Current						0	904
Disposal Group, Including Discontinued Operation, Liabilities, Current						0	777
Asset Retirement Obligation, Revision of Estimate							0
Impairment of Long-Lived Assets Held-for-use						201	50	510
Deconsolidation, Gain (Loss), Amount						0	0	$ 213
Exelon Generation Co L L C [Member] \| Operating Expense [Member]
Business Dispositions [Line Items]
Asset Retirement Obligation, Revision of Estimate						$ (150)
Exelon Generation Co L L C [Member] \| ExGen Texas Power [Member]
Business Dispositions [Line Items]
Impairment of Long-Lived Assets Held-for-use					$ 460
Generating Capacity \| GW						3.4
Deconsolidation, Gain (Loss), Amount		$ 213
Exelon Generation Co L L C [Member] \| Oyster Creek [Member]
Business Dispositions [Line Items]
Disposal Group, Including Discontinued Operation, Assets, Current							897
Disposal Group, Including Discontinued Operation, Liabilities, Current							$ 777
Exelon Generation Co L L C [Member] \| Oyster Creek [Member] \| Operating Expense [Member]
Business Dispositions [Line Items]
Asset Retirement Obligation, Revision of Estimate			$ 9	$ 84
Exelon Generation Co L L C [Member] \| Electrical Contracting Business [Member]
Business Dispositions [Line Items]
Proceeds from Divestiture of Businesses	$ 87