Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Fixed maturities, amortized cost	$ 8,502	$ 8,222
Equity securities, cost	2,471	2,369
Land, building and equipment, accumulated depreciation	$ 412	$ 397
Common stock, par value	$ 2	$ 2
Common stock, authorized	500	500
Common stock, issued	198	197
Common stock, outstanding	198	197
Treasury stock, shares	34	34