Asset Impairments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	$ 1	$ 8
Net income (loss) attributable to noncontrolling interests	25	(206)
Deferred income taxes and amortization of investment tax credits	(142)	(245)
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	1	8
Net income (loss) attributable to noncontrolling interests	24	(206)
Deferred income taxes and amortization of investment tax credits	(123)	$ (329)
Antelope Valley [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	0
Antelope Valley [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	0
Midwest Asset Group [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	0
Midwest Asset Group [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	$ 0