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, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
REVENUES
Investment income, net of expenses																	$ 531		$ 525		$ 518
Realized gains on investments																	42		70		159
Other revenue																	10		10		9
Total revenues	1,070	[1]	1,035	[1]	1,020	[1]	986	[1]	955	[1]	944	[1]	975	[1]	929	[1]	4,111	[1]	3,803	[1]	3,772
EXPENSES
Interest expense																	54		54		54
Other expenses																	14		13		16
Total benefits and expenses																	3,545		3,630		3,274
INCOME (LOSS) BEFORE INCOME TAXES AND EARNINGS OF SUBSIDIARIES	273		152		29		112		186		11		(99)		75		566		173		498
BENEFIT FOR INCOME TAXES																	145		9		123
NET INCOME	192		111		32		86		134		19		(50)		61		421		164		375
OTHER COMPREHENSIVE INCOME, BEFORE TAX
Unrealized gains on investments available-for-sale																	428		309		383
Reclassification adjustment for (gains) losses included in net income																	(42)		(70)		(159)
Unrealized gains on other																	(21)		(11)		(4)
Unrealized gains on investment availabl-for-sale, investments held by subsidiaries and other																	365		228		220
Amortization of pension actuarial (loss) gain and prior service costs																	13		25		(3)
Other comprehensive income before tax																	352		203		223
Income taxes on above of other comprehensive income																	124		71		78
Other comprehensive income, net of tax																	228		132		145
COMPREHENSIVE INCOME																	649		296		520
Cincinnati Financial Corporation [Member]
REVENUES
Investment income, net of expenses																	42		41		41
Realized gains on investments																	34		15		17
Other revenue																	15		14		14
Total revenues																	91		70		72
EXPENSES
Interest expense																	53		53		52
Other expenses																	27		25		24
Total benefits and expenses																	80		78		76
INCOME (LOSS) BEFORE INCOME TAXES AND EARNINGS OF SUBSIDIARIES																	11		(8)		(4)
BENEFIT FOR INCOME TAXES																	(4)		(9)		(7)
NET INCOME BEFORE EARNINGS OF SUBSIDIARIES																	15		1		3
Increase in equity of subsidiaries																	406		163		372
NET INCOME																	421		164		375
OTHER COMPREHENSIVE INCOME, BEFORE TAX
Unrealized gains on investments available-for-sale																	67		59		45
Unrealized gains on investments held by subsidiaries																	361		250		338
Reclassification adjustment for (gains) losses included in net income																	(34)		(15)		17
Reclassification adjustment for (gains) included in net income on subsidiaries																	(8)		(55)		(176)
Unrealized gains on other																	5		1		4
Unrealized losses on other subsidiaries																	(26)		(12)		(8)
Unrealized gains on investment availabl-for-sale, investments held by subsidiaries and other																	365		228		220
Amortization of pension actuarial (loss) gain and prior service costs																	(13)		(25)		3
Other comprehensive income before tax																	352		203		223
Income taxes on above of other comprehensive income																	124		71		78
Other comprehensive income, net of tax																	228		132		145
COMPREHENSIVE INCOME																	$ 649		$ 296		$ 520

[1] Revenues including realized investment gains and losses, which are integral to our financial results over the long term, may cause this value to fluctuate substantially because we have substantial discretion in the timing of investment sales. Also, applicable accounting standards require us to recognize gains and losses from certain changes in fair values of securities and embedded derivatives without actual realization of those gains and losses. We discuss realized investment gains for the past three years in Item 7, Investments Results of Operations, Page .