Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fixed-maturity securities held as available-for-sale, amortized cost	$ 6,444	$ 6,509
Investments held-to-maturity, fair value	2,635	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	281,670,699	281,352,782
Accumulated other comprehensive income (loss), taxes	4	7
Treasury stock, shares	98,097,072	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	217	441
Short-term investments held as available-for-sale, amortized cost	1,114	1,069
Other investments, fair value	13	13
Medium-term notes, financial instruments carried at fair value	180	197
Variable Interest Entity Primary Beneficiary [Member]
Investments held-to-maturity, fair value	2,635	2,632
Variable interest entity notes, financial instruments carried at fair value	$ 2,653	$ 2,047