Soliciting Material Soliciting Material Written Communications Written Communications Local Phone Number Local Phone Number Class of Stock [Domain] Class of Stock [Domain] Document Information [Line Items] Document Information [Line Items] Amendment Flag Amendment Flag Entity Emerging Growth Company Entity Emerging Growth Company Entity File Number Entity File Number Security Exchange Name Security Exchange Name Entity Address, State or Province Entity Address, State or Province Entity Address, Address Line One Entity Address, Address Line One City Area Code City Area Code 7 1/2% Debentures Due 2096 Seven And 1/2% Debentures Due 2096 [Member] 7 1/2% Debentures Due 2096 [Member] Cover [Abstract] Cover [Abstract] Document Period End Date Document Period End Date Document Information [Table] Document Information [Table] Pre-commencement Tender Offer Pre-commencement Tender Offer Class of Stock [Axis] Class of Stock [Axis] Entity Central Index Key Entity Central Index Key Pre-commencement Issuer Tender Offer Pre-commencement Issuer Tender Offer Entity Tax Identification Number Entity Tax Identification Number Entity Registrant Name Entity Registrant Name Trading Symbol Trading Symbol Common Stock Common Stock [Member] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Title of 12(b) Security Title of 12(b) Security Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Address, City or Town Entity Address, City or Town Document Type Document Type