Investments (Securities Available-For-Sale In A Gross Unrealized Loss Position) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated Fair Value of securities in a gross unrealized loss position, Less than 12 Months	$ 4,275	$ 7,327
Gross Unrealized Losses, Less than 12 months	211	260
Estimated Fair Value of securities in a gross unrealized loss position, Greater than 12 Months	1,923	3,414
Gross Unrealized Losses, Greater than 12 Months	330	544
Total Estimated Fair Value of securities in a gross unrealized loss position	6,198	10,741
Total Gross Unrealized Losses	541	804
Corporate And Other Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated Fair Value of securities in a gross unrealized loss position, Less than 12 Months	2,552	1,719
Gross Unrealized Losses, Less than 12 months	126	34
Estimated Fair Value of securities in a gross unrealized loss position, Greater than 12 Months	159	405
Gross Unrealized Losses, Greater than 12 Months	28	36
Total Estimated Fair Value of securities in a gross unrealized loss position	2,711	2,124
Total Gross Unrealized Losses	154	70
States, Municipalities And Political Subdivisions [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated Fair Value of securities in a gross unrealized loss position, Less than 12 Months	67	3,339
Gross Unrealized Losses, Less than 12 months	1	164
Estimated Fair Value of securities in a gross unrealized loss position, Greater than 12 Months	721	745
Gross Unrealized Losses, Greater than 12 Months	135	246
Total Estimated Fair Value of securities in a gross unrealized loss position	788	4,084
Total Gross Unrealized Losses	136	410
Residential Mortgage-Backed [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated Fair Value of securities in a gross unrealized loss position, Less than 12 Months	719	1,800
Gross Unrealized Losses, Less than 12 months	36	52
Estimated Fair Value of securities in a gross unrealized loss position, Greater than 12 Months	874	1,801
Gross Unrealized Losses, Greater than 12 Months	147	213
Total Estimated Fair Value of securities in a gross unrealized loss position	1,593	3,601
Total Gross Unrealized Losses	183	265
Commercial Mortgage-Backed [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated Fair Value of securities in a gross unrealized loss position, Less than 12 Months	431	164
Gross Unrealized Losses, Less than 12 months	39	3
Estimated Fair Value of securities in a gross unrealized loss position, Greater than 12 Months	169	333
Gross Unrealized Losses, Greater than 12 Months	20	38
Total Estimated Fair Value of securities in a gross unrealized loss position	600	497
Total Gross Unrealized Losses	59	41
Other Asset-Backed [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated Fair Value of securities in a gross unrealized loss position, Less than 12 Months	389	122
Gross Unrealized Losses, Less than 12 months	4	1
Estimated Fair Value of securities in a gross unrealized loss position, Greater than 12 Months		60
Gross Unrealized Losses, Greater than 12 Months		7
Total Estimated Fair Value of securities in a gross unrealized loss position	389	182
Total Gross Unrealized Losses	4	8
Asset-Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated Fair Value of securities in a gross unrealized loss position, Less than 12 Months	1,539	2,086
Gross Unrealized Losses, Less than 12 months	79	56
Estimated Fair Value of securities in a gross unrealized loss position, Greater than 12 Months	1,043	2,194
Gross Unrealized Losses, Greater than 12 Months	167	258
Total Estimated Fair Value of securities in a gross unrealized loss position	2,582	4,280
Total Gross Unrealized Losses	246	314
U.S. Treasury And Obligations Of Government-Sponsored Enterprises [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated Fair Value of securities in a gross unrealized loss position, Less than 12 Months		8
Gross Unrealized Losses, Less than 12 months		1
Total Estimated Fair Value of securities in a gross unrealized loss position		8
Total Gross Unrealized Losses		1
Fixed Maturity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated Fair Value of securities in a gross unrealized loss position, Less than 12 Months	4,158	7,152
Gross Unrealized Losses, Less than 12 months	206	255
Estimated Fair Value of securities in a gross unrealized loss position, Greater than 12 Months	1,923	3,344
Gross Unrealized Losses, Greater than 12 Months	330	540
Total Estimated Fair Value of securities in a gross unrealized loss position	6,081	10,496
Total Gross Unrealized Losses	536	795
Preferred Stock [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated Fair Value of securities in a gross unrealized loss position, Less than 12 Months	117	175
Gross Unrealized Losses, Less than 12 months	5	5
Estimated Fair Value of securities in a gross unrealized loss position, Greater than 12 Months		70
Gross Unrealized Losses, Greater than 12 Months		4
Total Estimated Fair Value of securities in a gross unrealized loss position	117	245
Total Gross Unrealized Losses	$ 5	$ 9