Investments (Details 3) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
U.S. government and agency fixed-income securities:
Short-term investments, principally at estimated fair value	$ 12,419	$ 9,384
Cash equivalents	4,900	9,600
United States [Member]
Government and agency fixed maturity securities:
Government and agency fixed maturity securities	35,565	33,304
Japan [Member]
Government and agency fixed maturity securities:
Government and agency fixed maturity securities	18,216	15,591
Mexico [Member]
Government and agency fixed maturity securities:
Government and agency fixed maturity securities	5,573	5,050
US Government Agencies Debt Securities [Member]
U.S. government and agency fixed-income securities:
Short-term investments, principally at estimated fair value	8,616	4,048
Cash equivalents	$ 1,570	$ 5,762

- Definition

Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash equivalents may be reported as cash equivalents, while legally restricted equivalents held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular equivalents should not be reported as part of unrestricted cash equivalents.

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