Impairment of Long-Lived Assets - Narrative (Details) $ in Millions	Mar. 31, 2019 USD ($)
Antelope Valley [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	$ 750
Exelon Generation Co L L C [Member] | Antelope Valley [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	750
ExGen Renewables IV, LLC [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	1,970
ExGen Renewables IV, LLC [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	$ 1,970