5.700% Subordinated Debentures due 2058 Subordinated Debentures Due 2058, 5.70% [Member] Subordinated Debentures Due 2058, 5.70% [Member] Entity Tax Identification Number Entity Tax Identification Number Entity File Number Entity File Number 4.250% Subordinated Debentures due 2060 Subordinated Debentures Due 2060, 4.25% [Member] Subordinated Debentures Due 2060, 4.25% Cover [Abstract] Cover [Abstract] Title of 12(b) Security Title of 12(b) Security Entities [Table] Entities [Table] Local Phone Number Local Phone Number Soliciting Material Soliciting Material Entity Address, Address Line One Entity Address, Address Line One Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 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 Entity Information [Line Items] Entity Information [Line Items] 5.75% Subordinated Debentures due 2056 Subordinated Debentures Due 2056, 5.75% [Member] Subordinated Debentures Due 2056, 5.75% [Member] Trading Symbol Trading Symbol 4.125% Subordinated Debentures due 2061 Subordinated Debentures Due 2061, 4.125% [Member] Subordinated Debentures Due 2061, 4.125% Debt Instrument [Axis] Debt Instrument [Axis] City Area Code City Area Code 5.100% Subordinated Debentures due 2059 Subordinated Debentures Due 2059, 5.10% [Member] Subordinated Debentures Due 2059, 5.10% [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 Security Exchange Name Security Exchange Name 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