Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Available-for-sale securities, at fair value:
Fixed maturity securities (amortized cost)	$ 90,083	$ 86,993
Equity securities (cost)		$ 247
Stockholders' Equity
Preferred stock - shares authorized (in shares)	10,000,000	10,000,000
Common stock - shares authorized (in shares)	800,000,000	800,000,000
Common stock - shares issued (in shares)	217,294,051	218,090,114
Common stock - shares outstanding (in shares)	217,294,051	218,090,114