|**Quarterly Supplementary Data (Tables)**    | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|-------------------------------------------- | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|
|**Notes To Financial Statements [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Unaudited Quarterly Financial Information    | This table includes unaudited quarterly financial information for the years ended December 31, 2013 and 2012:(Dollars in millions except per share data)Quarter1st2nd3rd4thFull year2013Revenues *$1,103$1,104$1,152$1,172$4,531Income before income taxes217148182167714Net income154110131122517Net income per common share—basic0.950.670.800.753.16Net income per common share—diluted0.940.660.790.743.122012Revenues *$986$1,020$1,035$1,070$4,111Income before income taxes11229152273566Net income8632111192421Net income per common share—basic0.530.200.691.182.59Net income per common share—diluted0.530.200.681.172.57
|                                            
|                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|(Dollars in millions except per share data)  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|2013                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Revenues *                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Income before income taxes                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Net income                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Net income per common share—basic            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Net income per common share—diluted          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|2012                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Revenues *                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Income before income taxes                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Net income                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Net income per common share—basic            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Net income per common share—diluted          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    

X- Details**Name:**
                    cinf_NotesToFinancialStatementsAbstract**Namespace Prefix:**
                    cinf_**Data Type:**
                    xbrli:stringItemType**Balance Type:**
                    na**Period Type:**
                    duration X- DefinitionTabular disclosure of the quarterly financial data in the annual financial statements. The disclosure includes financial information for each fiscal quarter for the current and previous year, including revenues, gross profit, income (loss) before extraordinary items and cumulative effect of a change in accounting principle and earnings per share data.+ ReferencesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a)-(j) -URI http://asc.fasb.org/extlink&oid=25249566&loc=d3e1280-108306+ Details**Name:**
                    us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock**Namespace Prefix:**
                    us-gaap_**Data Type:**
                    nonnum:textBlockItemType**Balance Type:**
                    na**Period Type:**
                    duration