Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fixed-maturity securities held as available-for-sale, amortized cost	$ 6,160	$ 6,509
Investments held-to-maturity, fair value	$ 2,401	$ 2,632
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	281,833,618	281,352,782
Accumulated other comprehensive income (loss), taxes	$ 51	$ 7
Treasury stock, shares	130,303,241	89,409,887
Non Variable Interest Entity [Member]
Fixed-maturity securities held as available-for-sale, amortized cost	$ 5,155	$ 5,036
Investments pledged as collateral, amortized cost	322	441
Short-term investments held as available-for-sale, amortized cost	720	1,069
Other investments, fair value	13	13
Medium-term notes, financial instruments carried at fair value	161	197
Variable Interest Entity Primary Beneficiary [Member]
Investments held-to-maturity, fair value	2,401	2,632
Variable interest entity notes, financial instruments carried at fair value	$ 2,362	$ 2,047