Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data	Sep. 30, 2011	Dec. 31, 2010
Short-term investments held as available-for-sale, amortized cost	$ 10,754	$ 12,822
Preferred stock, par value	$ 1	$ 1
Preferred stock, authorized shares	10,000,000	10,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$ 1	$ 1
Common stock, authorized shares	400,000,000	400,000,000
Common stock, issued shares	274,913,262	274,719,578
Accumulated other comprehensive loss, deferred tax	94	229
Treasury stock, shares	81,755,455	74,973,978
Non Variable Interest Entities [Member]
Fixed-maturity securities held as available-for-sale, amortized cost	7,874	9,679
Investments pledged as collateral, amortized cost	666	548
Short-term investments held as available-for-sale, amortized cost	1,486	2,073
Other investments, fair value	139	186
Property and equipment, accumulated depreciation	138	135
Medium-term notes, financial instruments carried at fair value	128	116
Variable Interest Entity, Primary Beneficiary [Member]
Investments held-to-maturity, fair value	3,492	3,760
Fixed-maturity securities held as available-for-sale, amortized cost	574	338
Variable interest entity notes, financial instruments carried at fair value	$ 5,123	$ 6,680