Intangible Assets - Schedule of Other Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross	$ 1,295	$ 1,267
Accumulated Amortization	(1,121)	(1,149)
Net	174	118
Exelon Generation Co L L C [Member] | Unamortized Energy Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	1,967	1,957
Accumulated Amortization	(1,612)	(1,588)
Net	355	369
Exelon Generation Co L L C [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	343	325
Accumulated Amortization	(190)	(162)
Net	153	163
Exelon Generation Co L L C [Member] | Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	243	243
Accumulated Amortization	(193)	(171)
Net	50	72
Commonwealth Edison Co [Member] | Intangible Asset Nineteen Ninety Nine Chicago Settlement Agreement [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	162	162
Accumulated Amortization	(155)	(148)
Net	7	14
Pepco Holdings LLC [Member] | Unamortized Energy Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	(1,515)	(1,515)
Accumulated Amortization	1,073	954
Net	(442)	(561)
Business Services Company [Member] | Licensing Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross	95	95
Accumulated Amortization	(44)	(34)
Net	$ 51	$ 61