Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Fixed maturities, amortized cost	$ 11,012	$ 10,643
Equity securities, cost	3,548	3,368
Land, building and equipment, accumulated depreciation	$ 269	$ 265
Common stock, par value	$ 2	$ 2
Common stock, authorized	500.0	500.0
Common stock, issued	198.3	198.3
Common stock, outstanding	198.3	198.3
Treasury stock, shares	34.9	35.5

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Face amount or stated value per share of common stock.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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