Condensed Financial Statements Of Parent Company Condensed Statements Of Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions
Net Income	$ 167	$ 183	$ 84	$ 91	$ 122	$ 131	$ 110	$ 154	$ 525	$ 517	$ 421
Unrealized gains on investments available-for-sale									250	299	251
Unrealized gains on investments available-for-sale, investments held by subsidiaries and other									388	494	365
Amortization of pension actuarial (loss) gain and prior service cost									(18)	83	(13)
Other comprehensive income before tax									370	577	352
Income taxes on above of other comprehensive income									130	202	124
Other comprehensive income, net of tax									240	375	228
Comprehensive Income									765	892	649
Cincinnati Financial Corporation
Condensed Financial Statements, Captions
Net Income									525	517	421
Unrealized gains on investments available-for-sale									150	303	67
Unrealized gains on investments held by subsidiaries									367	240	361
Reclassification adjustment for (gains) included in net income									(34)	(21)	(34)
Reclassification adjustment for (gains) included in net income on subsidiaries									(99)	(62)	(8)
Unrealized gains (losses) on other									7	(1)	5
Unrealized (losses) gains on other subsidiaries									$ (3)	$ 35	$ (26)