Supplemental Financial Information - Narrative (Details) - PECO Energy Co [Member] $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($)
Supplemental Financial Information Tables [Line Items]
Amount included in capital expenditures	$ 2
Smart Grid Grant Reimbursements	$ 5

Represents the reimbursable smart grid investment grant project expenditures included in capital expenditures.

No definition available.

Name:	exc_SmartGridGrantProjectCapitalExpenditures
Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration