Condensed Financial Statements Of Parent Company Condensed Balance Sheets (Parenthetical) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions
Fixed maturities, amortized cost	$ 10,643	$ 10,314
Equity securities, cost	3,368	3,094
Land, building and equipment, accumulated depreciation	265	253
Cincinnati Financial Corporation
Condensed Financial Statements, Captions
Fixed maturities, amortized cost	35	35
Equity securities, cost	1,282	1,159
Land, building and equipment, accumulated depreciation	$ 121	$ 115