Schedule I (Summary of Investments, Other than Investments in Related Parties) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	$ 8,900
Fair Value	8,693
Amount at which shown in the balance sheet	8,693
Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	8,755
Fair Value	8,566
Amount at which shown in the balance sheet	8,566
Other Aggregated Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	145
Fair Value	127
Amount at which shown in the balance sheet	127
Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	7,403
Fair Value	6,805
Amount at which shown in the balance sheet	7,159
Other Aggregated Investments [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	199
Fair Value	199
Amount at which shown in the balance sheet	199
Subtotal Long-Term Available-For-Sale [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	6,721
Fair Value	6,570
Amount at which shown in the balance sheet	6,570
Short Term Available-For-Sale [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,697
Fair Value	1,691
Amount at which shown in the balance sheet	1,691
Total Available-For-Sale [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	8,418
Fair Value	8,261
Amount at which shown in the balance sheet	8,261
Total Available-For-Sale [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	473
Fair Value	432
Amount at which shown in the balance sheet	432
Total Available-For-Sale [Member] | U.S. Treasury And Government Agency [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	783
Fair Value	822
Amount at which shown in the balance sheet	822
Total Available-For-Sale [Member] | Foreign Governments [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	264
Fair Value	286
Amount at which shown in the balance sheet	286
Total Available-For-Sale [Member] | Corporate Obligations [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,437
Fair Value	1,375
Amount at which shown in the balance sheet	1,375
Total Available-For-Sale [Member] | Corporate Obligations [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2
Fair Value	2
Amount at which shown in the balance sheet	2
Total Available-For-Sale [Member] | Taxable Bonds [Member] | State And Municipal Bonds [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	893
Fair Value	910
Amount at which shown in the balance sheet	910
Total Available-For-Sale [Member] | Tax-Exempt Bonds [Member] | State And Municipal Bonds [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,064
Fair Value	1,103
Amount at which shown in the balance sheet	1,103
Fair Value [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	337
Fair Value	305
Amount at which shown in the balance sheet	305
Fair Value [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	3,087
Fair Value	2,884
Amount at which shown in the balance sheet	2,884
Held-To-Maturity [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	3,843
Fair Value	3,489
Amount at which shown in the balance sheet	3,843
Asset-Backed Securities [Member] | Total Available-For-Sale [Member] | Collateralized Debt Obligations [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	250
Fair Value	133
Amount at which shown in the balance sheet	133
Asset-Backed Securities [Member] | Total Available-For-Sale [Member] | Collateralized Debt Obligations [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	112
Fair Value	97
Amount at which shown in the balance sheet	97
Asset-Backed Securities [Member] | Total Available-For-Sale [Member] | Other Asset-Backed [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	477
Fair Value	401
Amount at which shown in the balance sheet	401
Asset-Backed Securities [Member] | Total Available-For-Sale [Member] | Other Asset-Backed [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	41
Fair Value	41
Amount at which shown in the balance sheet	41
Asset-Backed Securities [Member] | Held-To-Maturity [Member] | Other Asset-Backed [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	3,843
Fair Value	3,489
Amount at which shown in the balance sheet	3,843
Mortgage-Backed Securities [Member] | Total Available-For-Sale [Member] | Residential Mortgage-Backed Securities [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,190
Fair Value	1,237
Amount at which shown in the balance sheet	1,237
Mortgage-Backed Securities [Member] | Total Available-For-Sale [Member] | Residential Mortgage-Backed Non-Agency [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	306
Fair Value	255
Amount at which shown in the balance sheet	255
Mortgage-Backed Securities [Member] | Total Available-For-Sale [Member] | Residential Mortgage-Backed Non-Agency [Member] | Consolidated VIEs [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	119
Fair Value	93
Amount at which shown in the balance sheet	93
Mortgage-Backed Securities [Member] | Total Available-For-Sale [Member] | Commercial Mortgage Backed [Member] | Fixed-Maturity Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	57
Fair Value	48
Amount at which shown in the balance sheet	$ 48