Intangible Assets Intangible Assets - Schedule of Finite-Lived Intangible Assets, Future Amortization Expense (Details) $ in Millions	Dec. 31, 2019 USD ($)
Finite-Lived Intangible Assets [Line Items]
2020	$ (13)
2021	2
2022	(21)
2023	(18)
2024	22
Exelon Generation Co L L C [Member]
Finite-Lived Intangible Assets [Line Items]
2020	85
2021	84
2022	58
2023	53
2024	50
Commonwealth Edison Co [Member]
Finite-Lived Intangible Assets [Line Items]
2020	7
2021	0
2022	0
2023	0
2024	0
Pepco Holdings LLC [Member]
Finite-Lived Intangible Assets [Line Items]
2020	(115)
2021	(92)
2022	(89)
2023	(81)
2024	$ (38)

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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