Shareholders' Equity And Dividend Restrictions (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Declared cash dividends, per share	$ 2.40	$ 2.24	$ 2.12
Dividend payment without prior regulatory approval, maximum percent of policyholder surplus	10.00%
Dividend payment without prior regulatory approval, percent of statutory net income for the prior calendar year	100.00%
Dividends might be paid during next year	$ 583
The Cincinnati Insurance Company
Cash Dividends Paid to Parent	550	$ 625	$ 500
Cincinnati Global
Cash Dividends Paid to Parent	$ 0	$ 0