Investments (Details 1) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Foreign corporate securities [Member] | Non-U.S. financial institutions [Member] | Fixed maturity securities [Member]
Summary of Perpetual Hybrid Securities
Estimated Fair Value	$ 1,094	$ 2,008
U.S. financial institutions [Member] | Fixed maturity securities [Member] | U.S. corporate securities [Member]
Summary of Perpetual Hybrid Securities
Estimated Fair Value	77	83
Non-redeemable preferred stock [Member] | Non-U.S. financial institutions [Member] | Equity Securities [Member]
Summary of Perpetual Hybrid Securities
Estimated Fair Value	841	1,043
Non-redeemable preferred stock [Member] | U.S. financial institutions [Member] | Equity Securities [Member]
Summary of Perpetual Hybrid Securities
Estimated Fair Value	$ 227	$ 236