Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Fixed maturities, amortized cost	$ 11,139	$ 11,108
Equity securities, cost	3,752	3,581
Land, building and equipment, accumulated depreciation	$ 280	$ 276
Common stock, par value	$ 2	$ 2
Common stock, authorized	500.0	500.0
Common stock, issued	198.3	198.3
Treasury stock, shares	37.5	35.4