Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Variable interest entity notes, financial instruments carried at fair value	$ 3,700
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	277,405,039	274,896,162
Accumulated other comprehensive income (loss), net of deferred tax	21	105
Treasury stock, shares	81,733,530	81,752,966
Non Variable Interest Entities [Member]
Fixed-maturity securities held as available-for-sale, amortized cost	4,347	6,259
Investments pledged as collateral, amortized cost	489	642
Short-term investments held as available-for-sale, amortized cost	662	1,577
Other investments, fair value	12	96
Property and equipment, accumulated depreciation	146	139
Medium-term notes, financial instruments carried at fair value	165	165
Variable Interest Entity [Member]
Investments held-to-maturity, fair value	2,674	3,489
Fixed-maturity securities held as available-for-sale, amortized cost	637	473
Variable interest entity notes, financial instruments carried at fair value	$ 3,659	$ 4,754