| **Supplementary Insurance Information**            | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   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| **Supplementary Insurance Information [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   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| Supplementary Insurance Information                | Schedule IIICincinnati Financial Corporation and SubsidiariesSupplementary Insurance Information(Dollars in millions) Years ended December 31,  2014 2013 2012Deferred policy acquisition costs:      Commercial lines insurance $257 $251 $235Personal lines insurance 108 104 93Excess and surplus lines insurance 14 11 9Total property casualty insurance 379 366 337Life insurance 199 199 133Total $578 $565 $470       Gross future policy benefits, losses, claims and expense losses:      Commercial lines insurance $3,797 $3,667 $3,645Personal lines insurance 439 417 398Excess and surplus lines insurance 202 157 126Total property casualty insurance 4,438 4,241 4,169Life insurance 2,519 2,441 2,341Total (1) $6,957 $6,682 $6,510       Gross unearned premiums:      Commercial lines insurance $1,441 $1,372 $1,246Personal lines insurance 562 535 490Excess and surplus lines insurance 78 67 54Total property casualty insurance 2,081 1,974 1,790Life insurance 1 2 2Total (1) $2,082 $1,976 $1,792       Other policy claims and benefits payable:      Commercial lines insurance $— $— $—Personal lines insurance — — —Excess and surplus lines insurance — — —Total property casualty insurance — — —Life insurance 25 19 15Total (1) $25 $19 $15       Earned premiums:      Commercial lines insurance $2,856 $2,636 $2,383Personal lines insurance 1,041 961 868Excess and surplus lines insurance 148 116 93Total property casualty insurance 4,045 3,713 3,344Life insurance 198 189 178Total $4,243 $3,902 $3,522        Schedule III (continued)Cincinnati Financial Corporation and SubsidiariesSupplementary Insurance Information(Dollars in millions) Years ended December 31,  2014 2013 2012Investment income, net of expenses:      Commercial lines insurance $— $— $—Personal lines insurance — — —Excess and surplus lines insurance — — —Total property casualty insurance (2) 358 348 351Life insurance 144 140 137Total $502 $488 $488       Benefits, claims losses and settlement expenses:      Commercial lines insurance $1,812 $1,596 $1,420Personal lines insurance 740 639 652Excess and surplus lines insurance 75 66 65Total property casualty insurance 2,627 2,301 2,137Life insurance 229 204 185Total $2,856 $2,505 $2,322       Amortization of deferred policy acquisition costs:      Commercial lines insurance $537 $514 $462Personal lines insurance 209 192 183Excess and surplus lines insurance 24 21 17Total property casualty insurance 770 727 662Life insurance 37 31 45Total (3) $807 $758 $707       Underwriting, acquisition and insurance expenses:      Commercial lines insurance $365 $343 $324Personal lines insurance 84 98 78Excess and surplus lines insurance 19 15 12Total property casualty insurance 468 456 414Life insurance 26 29 34Total (3) $494 $485 $448       Net written premiums:      Commercial lines insurance $2,922 $2,760 $2,459Personal lines insurance 1,068 1,005 918Excess and surplus lines insurance 153 128 105Total property casualty insurance 4,143 3,893 3,482Accident health insurance 3 2 3Total $4,146 $3,895 $3,485       Notes to Schedule III:(1) The sum of gross future policy benefits, losses, claims and expense losses, gross unearned premium and other policy claims and benefits payable is equal to the sum of Loss and loss expense reserves, Life policy reserves and investment contract reserves and Unearned premiums reported in the company’s consolidated balance sheets. (2) This segment information is not regularly allocated to segments and reviewed by company management in making decisions about resources to be allocated to the segments or to assess their performance.(3) The sum of amortization of deferred policy acquisition costs and other underwriting and insurance expenses is equal to Underwriting, acquisition and insurance expenses in the consolidated statements of income.  |

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| - Definition
The entire disclosure for required supplementary insurance information giving segment detail in support of various balance sheet and income statement captions. The balance sheet information generally is presented as of the date of each audited balance sheet filed, and the income statement information generally is presented for each period for which an audited income statement is required to be filed. Supplementary insurance information table includes segment name; deferred policy acquisition costs; future policy benefits, losses, claims and loss expenses; unearned premiums; other policy claims and benefits payable; premium revenue; net investment income; benefits, claims, losses and settlement expenses; amortization of deferred policy acquisition costs; other operating expenses; and premiums written.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 16 -Article 12Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 05 -Paragraph c -Article 7Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574960-122915Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.7-05.(c) Schedule III) -URI http://asc.fasb.org/extlink&oid=6879921&loc=d3e569147-122900
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