Investments (Securities Available-For-Sale In A Gross Unrealized Loss Position) (Details) (USD $) In Millions	Sep. 30, 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	$ 5,218	$ 7,327
Gross unrealized losses, less than 12 months	213	260
Estimated fair value of securities in a gross unrealized loss position, greater than 12 months	2,111	3,414
Gross unrealized losses, greater than 12 months	343	544
Total estimated fair value of securities in a gross unrealized loss position	7,329	10,741
Total gross unrealized losses	556	804
Available-For-Sale [Member] | Preferred Stock [Member] | Equity 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	129	175
Gross unrealized losses, less than 12 months	7	5
Estimated fair value of securities in a gross unrealized loss position, greater than 12 months	19	70
Gross unrealized losses, greater than 12 months	1	4
Total estimated fair value of securities in a gross unrealized loss position	148	245
Total gross unrealized losses	8	9
Available-For-Sale [Member] | 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	5,053	7,152
Gross unrealized losses, less than 12 months	204	255
Estimated fair value of securities in a gross unrealized loss position, greater than 12 months	2,092	3,344
Gross unrealized losses, greater than 12 months	342	540
Total estimated fair value of securities in a gross unrealized loss position	7,145	10,496
Total gross unrealized losses	546	795
Residential Mortgage-Backed [Member] | Fixed Maturity Securities [Member] | 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	789	1,800
Gross unrealized losses, less than 12 months	20	52
Estimated fair value of securities in a gross unrealized loss position, greater than 12 months	978	1,801
Gross unrealized losses, greater than 12 months	141	213
Total estimated fair value of securities in a gross unrealized loss position	1,767	3,601
Total gross unrealized losses	161	265
Commercial Mortgage-Backed [Member] | Fixed Maturity Securities [Member] | 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	474	164
Gross unrealized losses, less than 12 months	42	3
Estimated fair value of securities in a gross unrealized loss position, greater than 12 months	179	333
Gross unrealized losses, greater than 12 months	19	38
Total estimated fair value of securities in a gross unrealized loss position	653	497
Total gross unrealized losses	61	41
Other Asset-Backed [Member] | Fixed Maturity Securities [Member] | 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	377	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	77	60
Gross unrealized losses, greater than 12 months	10	7
Total estimated fair value of securities in a gross unrealized loss position	454	182
Total gross unrealized losses	14	8
Fixed Maturity Securities [Member] | 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	1,640	2,086
Gross unrealized losses, less than 12 months	66	56
Estimated fair value of securities in a gross unrealized loss position, greater than 12 months	1,234	2,194
Gross unrealized losses, greater than 12 months	170	258
Total estimated fair value of securities in a gross unrealized loss position	2,874	4,280
Total gross unrealized losses	236	314
Fixed Maturity Securities [Member] | 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
States, Municipalities And Political Subdivisions [Member] | 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	270	3,339
Gross unrealized losses, less than 12 months	4	164
Estimated fair value of securities in a gross unrealized loss position, greater than 12 months	716	745
Gross unrealized losses, greater than 12 months	146	246
Total estimated fair value of securities in a gross unrealized loss position	986	4,084
Total gross unrealized losses	150	410
Corporate And Other Bonds [Member] | 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	3,143	1,719
Gross unrealized losses, less than 12 months	134	34
Estimated fair value of securities in a gross unrealized loss position, greater than 12 months	142	405
Gross unrealized losses, greater than 12 months	26	36
Total estimated fair value of securities in a gross unrealized loss position	3,285	2,124
Total gross unrealized losses	160	70
Common Stock [Member] | Equity 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	36
Gross unrealized losses, less than 12 months	2
Total estimated fair value of securities in a gross unrealized loss position	36
Total gross unrealized losses	$ 2