Entity Tax Identification Number Entity Tax Identification Number Entity Address, Address Line Two Entity Address, Address Line Two Entity File Number Entity File Number Legal Entity [Axis] Legal Entity [Axis] Cover page. Cover [Abstract] Title of 12(b) Security Title of 12(b) Security Local Phone Number Local Phone Number Soliciting Material Soliciting Material Entity Address, Address Line One Entity Address, Address Line One Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Entity Address, State or Province Entity Address, State or Province Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Written Communications Written Communications Trading Symbol Trading Symbol City Area Code City Area Code Document Information [Table] Document Information [Table] Commonwealth Edison Co Commonwealth Edison Co [Member] Commonwealth Edison Co [Member] Document Period End Date Document Period End Date Amendment Flag Amendment Flag Pre-commencement Issuer Tender Offer Pre-commencement Issuer Tender Offer Entity Address, City or Town Entity Address, City or Town Entity [Domain] Entity [Domain] Security Exchange Name Security Exchange Name Document Information [Line Items] Document Information [Line Items] Document Type Document Type Pre-commencement Tender Offer Pre-commencement Tender Offer Entity Central Index Key Entity Central Index Key Entity Emerging Growth Company Entity Emerging Growth Company