Early Plant Retirements - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Operating Expenses	$ 30,240	$ 30,096	$ 32,143
Depreciation and Amortization	5,014	4,252	4,353
Midwest Asset Group [Member] | Facility Closing [Member]
Property, Plant and Equipment [Line Items]
Severance Costs	81
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Depreciation and Amortization	$ 2,123	$ 1,535	$ 1,797
Exelon Generation Co L L C [Member] | Salem [Member] | Nuclear Plant [Member]
Property, Plant and Equipment [Line Items]
Ownership interest	42.59%
Exelon Generation Co L L C [Member] | Midwest Asset Group [Member] | Facility Closing [Member]
Property, Plant and Equipment [Line Items]
Severance Costs	$ 81
Exelon Generation Co L L C [Member] | Generation New England [Member]
Property, Plant and Equipment [Line Items]
Operating Expenses	22
Depreciation and Amortization	$ 26