Investments and Cash (Details 5) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Amortized Cost
Due within one year	$ 152
Due after one year through five years	1,623
Due after five years through 10 years	2,328
Due after 10 years	3,576
Estimated Fair Value
Due within one year	153
Due after one year through five years	1,700
Due after five years through 10 years	2,527
Due after 10 years	3,904
Estimated fair value	9,985	10,056
Fixed maturity securities held under trust for the benefit of reinsured companies	371	368
Eligible securities deposited for the benefit of policyholders	24	27
Percentage of the value of letter of credit of fixed maturity investments held in segregated account as collateral for letter of credit	120.00%
Fixed maturity investments in a segregated portfolio primarily to provide collateral for a LOC	3.5	3.5
Fair market value of company's pledged securities	709	660
Fair value of the securities purchased to mitigate insured losses	629	670
RMBS
Amortized Cost
Amortized cost	1,210
Estimated Fair Value
Estimated fair value	1,196
CMBS
Amortized Cost
Amortized cost	474
Estimated Fair Value
Estimated fair value	505
Fixed maturity securities
Amortized Cost
Amortized cost	9,363	9,346
Estimated Fair Value
Estimated fair value	$ 9,985

Fair value of securities held for the protection of policyholders in fulfillment of state licensing requirements.

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