Document Type Document Type Entity Listings, Exchange [Axis] Entity Listings, Exchange [Axis] Document Information [Line Items] Document Information [Line Items] Series I Preferred Stock Series I Preferred Stock [Member] Series I Preferred Stock Amendment Flag Amendment Flag City Area Code City Area Code Entity Address, State or Province Entity Address, State or Province Soliciting Material Soliciting Material Document Period End Date Document Period End Date Entity Tax Identification Number Entity Tax Identification Number Common Stock Common Stock [Member] Pre-commencement Tender Offer Pre-commencement Tender Offer Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Exchange [Domain] Exchange [Domain] Class of Stock [Domain] Class of Stock [Domain] NEW YORK STOCK EXCHANGE, INC. NEW YORK STOCK EXCHANGE, INC. [Member] Class of Stock [Axis] Class of Stock [Axis] Entity File Number Entity File Number Entity Central Index Key Entity Central Index Key Trading Symbol Trading Symbol Entity Address, Postal Zip Code Entity Address, Postal Zip Code Local Phone Number Local Phone Number Written Communications Written Communications Title of 12(b) Security Title of 12(b) Security Series G Preferred Stock Series G Preferred Stock [Member] Security Exchange Name Security Exchange Name Entity Address, City or Town Entity Address, City or Town Cover [Abstract] Cover [Abstract] Pre-commencement Issuer Tender Offer Pre-commencement Issuer Tender Offer Series H Preferred Stock Series H Preferred Stock [Member] Entity Address, Address Line One Entity Address, Address Line One Entity Emerging Growth Company Entity Emerging Growth Company Entity Registrant Name Entity Registrant Name Subordinated Debentures Due 2053 at 5.10 Percent Subordinated Debentures Due 2053 at 5.10 Percent [Member] Represents the subordinated debentures due in 2053 at an interest rate of 5.10 percent. CHICAGO STOCK EXCHANGE, INC CHICAGO STOCK EXCHANGE, INC [Member] Document Information [Table] Document Information [Table]