Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 568	$ 268	$ (222)
Derivative Liability, Current	(18)	(33)
Derivative Liability, Noncurrent	(201)	(268)
Commonwealth Edison Co [Member]
Derivative [Line Items]
Derivative Liability, Current	(18)	(33)
Derivative Liability, Noncurrent	(201)	(268)
Not Designated as Hedging Instrument, Economic Hedge [Member] \| Commodity Contract [Member] \| Commonwealth Edison Co [Member]
Derivative [Line Items]
Derivative Liability, Current	(18)	(33)
Derivative Liability, Noncurrent	(201)	(268)
Derivative Liability	$ (219)	$ (301)

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

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