Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Fixed maturities, available for sale at amortized cost	$ 31,565	$ 29,074
Equity securities, available for sale at cost	$ 1,469	$ 1,283
Common Stock, par value (USD per share)	$ 0	$ 0
Common Stock, shares authorized	200,000,000	200,000,000
Common Stock, shares outstanding	87,474,452	87,708,793