Supplemental Financial Information - Narrative (Details) - PECO Energy Co [Member] - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Net	$ 9	$ 9
Financing Receivable, Allowance for Credit Losses	11	13
Low To Medium Risk [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses	0	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	$ 8	$ 9