Early Plant Retirements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization	$ 1,289	$ 1,083	$ 3,312	$ 3,237
Operating Expenses	8,087	7,559	22,387	22,703
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization	$ 558	$ 407	$ 1,161	$ 1,221
Salem [Member] | Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Ownership interest	42.59%		42.59%
Midwest Asset Group [Member]
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization			$ 6
Generation New England [Member]
Property, Plant and Equipment [Line Items]
Operating Expenses			43
Generation New England [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization			6
Operating Expenses			43
Facility Closing [Member] | Midwest Asset Group [Member]
Property, Plant and Equipment [Line Items]
Operating Expenses			81
Facility Closing [Member] | Midwest Asset Group [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Operating Expenses			$ 81