Income Taxes - Summary of Interest Receivable (Payable) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Net interest receivable (payable) recognized related to uncertain tax positions	$ (288)	$ (310)
Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Net interest receivable (payable) recognized related to uncertain tax positions	80	40
Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Net interest receivable (payable) recognized related to uncertain tax positions	(210)	(203)
PECO Energy Co [Member]
Income Taxes [Line Items]
Net interest receivable (payable) recognized related to uncertain tax positions	3	3
Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Net interest receivable (payable) recognized related to uncertain tax positions	$ (1)	$ (1)