Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fixed-maturity securities held as available-for-sale, amortized cost	$ 6,509	$ 6,824
Investments held-to-maturity, fair value	2,632	2,651
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	281,352,782	277,812,430
Accumulated other comprehensive income (loss), taxes	7	54
Treasury stock, shares	89,409,887	85,562,546
Non Variable Interest Entity [Member]
Fixed-maturity securities held as available-for-sale, amortized cost	5,036	5,064
Investments pledged as collateral, amortized cost	441	483
Short-term investments held as available-for-sale, amortized cost	1,069	1,203
Other investments, fair value	13	11
Medium-term notes, financial instruments carried at fair value	197	203
Variable Interest Entity Primary Beneficiary [Member]
Fixed-maturity securities held as available-for-sale, amortized cost	0	136
Investments held-to-maturity, fair value	2,632	2,651
Variable interest entity notes, financial instruments carried at fair value	$ 2,047	$ 2,356