Early Plant Retirements - Pretax Expense (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Asset Retirement Obligation, Revision of Estimate			$ 20
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Revision of Estimate			0
Exelon Generation Co L L C [Member] \| Facility Closing [Member] \| Three Mile Island [Member]
Accelerated depreciation		$ 216
Accelerated nuclear fuel amortization		13
Restructuring and Related Cost, Incurred Cost		176
Asset Retirement Obligation, Revision of Estimate		(53)
Exelon Generation Co L L C [Member] \| Facility Closing [Member] \| TMI, Oyster Creek [Member]
Accelerated depreciation		216	539
Accelerated nuclear fuel amortization		13	57
Operating and maintenance		0	32
Restructuring and Related Cost, Incurred Cost		176	628
Asset Retirement Obligation, Revision of Estimate		(53)	0
Asset Retirement Obligation Contractual Offset		$ 0	$ 0
Exelon Generation Co L L C [Member] \| Facility Closing [Member] \| Byron Dresden [Member]
Accelerated depreciation	$ 895
Accelerated nuclear fuel amortization	60
Operating and maintenance	255
Restructuring and Related Cost, Incurred Cost	880
Asset Retirement Obligation, Revision of Estimate	34
Asset Retirement Obligation Contractual Offset	$ (364)

Asset Retirement Obligation Contractual Offset

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- Definition

The amount of capitalized nuclear fuel costs that are charged to fuel expense during the period using the unit-of-production method.

+ References

No definition available.

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- Definition

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.

+ References

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The total amount of other operating cost and expense items that are associated with the entity's normal revenue producing operation.

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Discloses the amount charged against the accrued restructuring reserves, or earnings if not previously accrued, during the period for the specified type of restructuring cost.

+ References

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Amount of accelerated depreciation charged against earnings associated with exit from or disposal of business activities or restructuring plan.

+ References

No definition available.

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