Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Fixed income securities, at fair value, amortized cost (in dollars)	$ 56,293	$ 57,134
Equity securities, at fair value, cost (in dollars)	6,568	4,489
Short-term, at fair value, amortized cost (in dollars)	$ 4,256	$ 3,027
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	92,500	79,800
Preferred stock, shares outstanding (in shares)	92,500	79,800
Preferred stock, shares aggregate liquidation preference (in dollars)	$ 2,313	$ 1,995
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	2,000,000,000.0	2,000,000,000.0
Common stock, shares issued (in shares)	900,000,000	900,000,000
Common stock, shares outstanding (in shares)	319,000,000	332,000,000
Treasury stock, shares (in shares)	581,000,000	568,000,000