Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Income Tax Contingency
Tax at statutory rate, percentage	21.00%	21.00%	21.00%	21.00%
Gross unrecognized tax benefits released		$ 34
Deferred tax assets valuation allowance	$ 0		$ 0		$ 0
Cincinnati Global
Income Tax Contingency
Decrease in deferred tax assets	10		20
Decrease in deferred tax valuation allowance	10		20
Net deferred tax assets	11		11
Deferred tax assets valuation allowance	11		11
Cincinnati Global | United States
Income Tax Contingency
Operating loss carryforwards	6		6		5
Cincinnati Global | United Kingdom
Income Tax Contingency
Operating loss carryforwards	$ 99		$ 99		$ 109