Consolidated Balance Sheet (Unaudited) (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Fixed maturities, available for sale at amortized cost	$ 22,755	$ 22,083
Equity securities, at cost	$ 837	$ 778
Common Stock, par value
Common Stock, shares authorized	200,000,000	200,000,000
Common Stock, shares outstanding	89,883,222	88,979,303