Consolidated Balance Sheet (Unaudited) (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Fixed maturities, available for sale at amortized cost	$ 36,231	$ 33,735
Equity securities, available for sale at cost	$ 1,338	$ 1,351
Common Stock, par value (USD per share)	$ 0	$ 0
Common Stock, shares authorized	200,000,000	200,000,000
Common Stock, shares outstanding	88,007,252	86,924,399