Condensed Financial Statements Of Parent Company Condensed Statements Of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions
Net Income	$ 100	$ 180	$ 123	$ 188	$ 156	$ 174	$ 176	$ 128	$ 591	$ 634	$ 525
Unrealized gains and (losses) on investments available for sale									345	(405)	250
Unrealized gains and (losses) on investments available for sale, investments held by subsidiaries and other									521	(612)	388
Amortization of pension actuarial gains (losses) and prior service cost									16	(6)	(18)
Other comprehensive income (loss) before tax									537	(618)	370
Income taxes on above of other comprehensive income (loss)									188	(218)	130
Other comprehensive income (loss), net of tax									349	(400)	240
Comprehensive Income									940	234	765
Cincinnati Financial Corporation
Condensed Financial Statements, Captions
Net Income									591	634	525
Unrealized gains and (losses) on investments available for sale									221	(111)	150
Unrealized gains and (losses) on investments held by subsidiaries									434	(444)	367
Reclassification adjustment for (losses) and gains included in net income									(27)	19	(34)
Reclassification adjustment for (gains) included in net income on subsidiaries									(97)	(89)	(99)
Unrealized (losses) and gains on other									(6)	0	7
Unrealized (losses) and gains on other subsidiaries									$ (4)	$ 13	$ (3)