Condensed Financial Statements Of Parent Company Condensed Statements Of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Investment income, net of expenses									$ 646	$ 619	$ 609
Investment gains and losses, net									1,650	(402)	148
Other revenues									9	5	5
Total revenues	$ 2,152	$ 1,700	$ 1,913	$ 2,159	$ 710	$ 1,915	$ 1,558	$ 1,224	7,924	5,407	5,732
Expenses
Interest expense									53	53	53
Other expenses									23	16	13
Total expenses									5,452	5,156	5,002
Income (Loss) Before Income Taxes and Earnings of Subsidiaries	781	294	530	867	(581)	618	264	(50)	2,472	251	730
Provision (Benefit) for Income Taxes									475	(36)	(315)
Net Income	$ 626	$ 248	$ 428	$ 695	$ (452)	$ 553	$ 217	$ (31)	1,997	287	1,045
Change in unrealized gain (loss) on securities									0	(2)	235
Amortization of pension actuarial gains and losses and prior service costs									5	(3)	7
Other Comprehensive Income (Loss) Before Other Comprehensive Income (Loss) from Subsidiaries									5	(5)	242
Other Comprehensive Income (Loss) of subsidiaries									421	(258)	361
Other comprehensive income (loss)									426	(263)	603
Comprehensive Income									2,423	24	1,648
Cincinnati Financial Corporation
Revenues
Investment income, net of expenses									75	65	62
Investment gains and losses, net									728	(108)	28
Other revenues									15	15	15
Total revenues									818	(28)	105
Expenses
Interest expense									52	52	52
Other expenses									37	31	28
Total expenses									89	83	80
Income (Loss) Before Income Taxes and Earnings of Subsidiaries									729	(111)	25
Provision (Benefit) for Income Taxes									146	(31)	(161)
Net Income (Loss) Before Earnings of Subsidiaries									583	(80)	186
Increase in equity of subsidiaries									1,414	367	859
Net Income									$ 1,997	$ 287	$ 1,045