Supplemental Financial Information - Narrative (Details) - PECO Energy Co [Member] - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Net	$ 11	$ 9
Financing Receivable, Allowance for Credit Losses	12	13
Low To Medium Risk [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses		1
Risk Level, Medium [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses	3	3
Risk Level, High [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses	$ 9	$ 9