Fair Values of Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Carrying values and fair values of financial instruments [Abstract]
Short term investments	$ 1,893	$ 1,905
Fixed maturities	37,184	36,519
Equity securities	1,512	1,550
Long Term Debt	3,575	3,975
Carrying Value [Member]
Carrying values and fair values of financial instruments [Abstract]
Short term investments	1,893	1,905
Fixed maturities	37,184	36,519
Equity securities	1,512	1,550
Long Term Debt	3,575	3,975
Fair Value [Member]
Carrying values and fair values of financial instruments [Abstract]
Short term investments	1,893	1,905
Fixed maturities	37,184	36,519
Equity securities	1,512	1,550
Long Term Debt	$ 4,085	$ 4,318

For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

For an unclassified balance sheet, this item represents equity securities categorized neither as held-to-maturity nor trading.

+ References

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+ Details

- Definition

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date. May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

+ References+ Details

- Definition

Other investments not otherwise specified in the taxonomy that will be realized in a short period of time, usually less than one year or the normal operating cycle, whichever is longer.

+ References+ Details