Early Plant Retirements - Pretax Expense (Details) - Facility Closing [Member] - Byron Dresden - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021
Accelerated depreciation	$ 611	$ 1,230
Accelerated nuclear fuel amortization	52	106
Operating and maintenance	2	4
Asset Retirement Obligation Contractual Offset	(166)	(391)
Restructuring and Related Cost, Incurred Cost	499	949
Exelon Generation Co L L C [Member]
Accelerated depreciation	611	1,230
Accelerated nuclear fuel amortization	52	106
Operating and maintenance	2	4
Asset Retirement Obligation Contractual Offset	(166)	(391)
Restructuring and Related Cost, Incurred Cost	$ 499	$ 949