Investments (Details 1) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
U.S. corporate securities [Member] | Fixed maturity securities [Member] | U.S. financial institutions [Member]
Summary of Perpetual Hybrid Securities
Estimated Fair Value	$ 181	$ 83
Foreign corporate securities [Member] | Fixed maturity securities [Member] | Non-U.S. financial institutions [Member]
Summary of Perpetual Hybrid Securities
Estimated Fair Value	632	2,008
Non-redeemable preferred stock [Member] | Equity Securities [Member] | Non-U.S. financial institutions [Member]
Summary of Perpetual Hybrid Securities
Estimated Fair Value	481	1,043
Non-redeemable preferred stock [Member] | Equity Securities [Member] | U.S. financial institutions [Member]
Summary of Perpetual Hybrid Securities
Estimated Fair Value	$ 381	$ 236