Investments (Analysis Of Cost Or Amortized Cost Gross Unrealized Gains And Losses And Fair Value For Investments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
States, Municipalities And Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		$ 3,006
Gross Unrealized Gains		246
Fair Value		3,252
Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,270
Gross Unrealized Gains	977
Gross Unrealized Losses	9
Fair Value	3,238
Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	8,222	8,084
Gross Unrealized Gains	874	713
Gross Unrealized Losses	3	18
Fair Value	9,093	8,779
Fixed Maturities [Member] | States, Municipalities And Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,040
Gross Unrealized Gains	250
Gross Unrealized Losses	1
Fair Value	3,289
Fixed Maturities [Member] | Convertibles And Bonds With Warrants Attached [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	31	59
Fair Value	31	59
Fixed Maturities [Member] | United States Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	7	6
Gross Unrealized Gains	1	1
Fair Value	8	7
Fixed Maturities [Member] | Government-Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	164	159
Gross Unrealized Gains		1
Fair Value	164	160
Fixed Maturities [Member] | Foreign Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3	3
Fair Value	3	3
Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	27
Gross Unrealized Gains	1
Fair Value	28
Fixed Maturities [Member] | Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,950	4,851
Gross Unrealized Gains	622	465
Gross Unrealized Losses	2	18
Fair Value	5,570	5,298
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,369	2,162
Gross Unrealized Gains	1,014	829
Gross Unrealized Losses	10	35
Fair Value	3,373	2,956
Equity Securities [Member] | Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost		2,088
Gross Unrealized Gains		801
Gross Unrealized Losses		35
Fair Value		2,854
Equity Securities [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	99	74
Gross Unrealized Gains	37	28
Gross Unrealized Losses	1
Fair Value	135	102
Fixed Maturities And Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	10,591	10,246
Gross Unrealized Gains	1,888	1,542
Gross Unrealized Losses	13	53
Fair Value	$ 12,466	$ 11,735