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Investments (Distribution Of Contractual Maturity Available For Sale) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 9,025	$ 12,822
Fair Value	8,810	12,238
Fixed-Maturity Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, Amortized Cost	639
Due in one year or less, Fair Value	640
Due after one year through five years, Amortized Cost	1,451
Due after one year through five years, Fair Value	1,465
Due after five years through ten years, Amortized Cost	683
Due after five years through ten years, Fair Value	707
Due after ten years through fifteen years, Amortized Cost	578
Due after ten years through fifteen years, Fair Value	583
Due after fifteen years, Amortized Cost	1,789
Due after fifteen years, Fair Value	1,801
Amortized Cost	7,492	11,699
Fair Value	7,336	11,115
Fixed-Maturity Investments [Member] | Variable Interest Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Due after one year through five years, Amortized Cost	2
Due after one year through five years, Fair Value	2
Amortized Cost	274
Fair Value	233
Asset-Backed Securities [Member] | Fixed-Maturity Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	771
Fair Value	573
Asset-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Variable Interest Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	153
Fair Value	138
Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,581
Fair Value	1,567
Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member] | Variable Interest Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	119
Fair Value	$ 93

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