Condensed Financial Statements Of Parent Company Condensed Statements Of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Investment income, net of expenses									$ 619	$ 609	$ 595
Investment gains and losses, net									(402)	148	124
Other revenues									5	5	5
Total revenues	$ 710	$ 1,915	$ 1,558	$ 1,224	$ 1,411	$ 1,412	$ 1,386	$ 1,523	5,407	5,732	5,449
Expenses
Interest expense									53	53	53
Other expenses									16	13	12
Total expenses									5,156	5,002	4,637
Income (Loss) Before Income Taxes and Earnings of Subsidiaries	(581)	618	264	(50)	197	129	128	276	251	730	812
Benefit for income taxes									(36)	(315)	221
Net Income	$ (452)	$ 553	$ 217	$ (31)	$ 642	$ 102	$ 100	$ 201	287	1,045	591
Cincinnati Financial Corporation
Revenues
Investment income, net of expenses									65	62	56
Investment gains and losses, net									(108)	28	27
Other revenues									15	15	15
Total revenues									(28)	105	98
Expenses
Interest expense									52	52	52
Other expenses									31	28	27
Total expenses									83	80	79
Income (Loss) Before Income Taxes and Earnings of Subsidiaries									(111)	25	19
Benefit for income taxes									(31)	(161)	(6)
Net Income (Loss) Before Earnings of Subsidiaries									(80)	186	25
Increase in equity of subsidiaries									367	859	566
Net Income									$ 287	$ 1,045	$ 591