Fair Value Measurements (Fair Value Hierarchy For Assets Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	$ 9,093	$ 8,779
Available for sale securities, equity securities	3,373	2,956
Separate accounts	734	671
Fair value of asset	13,164	12,371
Top Hat Savings Plan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	9	8
Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	9,093	8,779
Fixed Maturities [Member] | States, Municipalities And Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	3,289	3,252
Fixed Maturities [Member] | Convertibles And Bonds With Warrants Attached [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	31	59
Fixed Maturities [Member] | United States Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	8	7
Fixed Maturities [Member] | Government-Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	164	160
Fixed Maturities [Member] | Foreign Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	3	3
Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	28
Fixed Maturities [Member] | Corporate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	5,570	5,298
Equity Securities [Member] | Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, equity securities	3,238	2,854
Equity Securities [Member] | Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, equity securities	135	102
Taxable Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Separate accounts	689	628
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of asset	3,255	2,869
Fair Value, Inputs, Level 1 [Member] | Top Hat Savings Plan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	9	8
Fair Value, Inputs, Level 1 [Member] | Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	8	7
Fair Value, Inputs, Level 1 [Member] | Fixed Maturities [Member] | United States Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	8	7
Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member] | Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, equity securities	3,238	2,854
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of asset	9,904	9,477
Fair Value, Inputs, Level 2 [Member] | Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	9,081	8,751
Fair Value, Inputs, Level 2 [Member] | Fixed Maturities [Member] | States, Municipalities And Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	3,288	3,249
Fair Value, Inputs, Level 2 [Member] | Fixed Maturities [Member] | Convertibles And Bonds With Warrants Attached [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	31	59
Fair Value, Inputs, Level 2 [Member] | Fixed Maturities [Member] | Government-Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	164	160
Fair Value, Inputs, Level 2 [Member] | Fixed Maturities [Member] | Foreign Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	3	3
Fair Value, Inputs, Level 2 [Member] | Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	28
Fair Value, Inputs, Level 2 [Member] | Fixed Maturities [Member] | Corporate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	5,567	5,280
Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, equity securities	134	98
Fair Value, Inputs, Level 2 [Member] | Taxable Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Separate accounts	689	628
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of asset	5	25
Fair Value, Inputs, Level 3 [Member] | Fixed Maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	4	21
Fair Value, Inputs, Level 3 [Member] | Fixed Maturities [Member] | States, Municipalities And Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	1	3
Fair Value, Inputs, Level 3 [Member] | Fixed Maturities [Member] | Corporate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, debt Securities	3	18
Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member] | Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, equity securities	$ 1	$ 4