Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fixed-maturity securities held as available-for-sale, amortized cost	$ 6,443	$ 6,122
Investments held-to-maturity, fair value	2,566	2,674
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	277,804,062	277,405,039
Accumulated other comprehensive loss, net of tax	30	21
Treasury stock, shares	85,551,418	81,733,530
Non Variable Interest Entity [Member]
Fixed-maturity securities held as available-for-sale, amortized cost	4,516	4,347
Investments pledged as collateral, amortized cost	407	489
Short-term investments held as available-for-sale, amortized cost	1,377	662
Other investments, fair value	10	12
Property and equipment, accumulated depreciation	87	146
Medium-term notes, financial instruments carried at fair value	204	165
Variable Interest Entity Primary Beneficiary [Member]
Fixed-maturity securities held as available-for-sale, amortized cost	156	637
Investments held-to-maturity, fair value	2,566	2,674
Variable interest entity notes, financial instruments carried at fair value	$ 2,426	$ 3,659