Employee Retirement Benefits (Fair Value Hierarchy Of Assets Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, debt Securities	$ 9,093	$ 8,779
Available for sale securities, equity securities	3,373	2,956
Fair value of asset	13,164	12,371
Fixed Maturities [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, debt Securities	60	59
Fixed Maturities [Member] \| Corporate Fixed Maturities [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, debt Securities	24	25
Fixed Maturities [Member] \| States, Municipalities And Political Subdivisions [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, debt Securities	36	34
Equity Securities [Member] \| Common Stock [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, equity securities	175	149
Equity Securities [Member] \| Preferred Stock [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, equity securities		4
Fixed Maturities And Equity Securities [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Fair value of asset	235	212
Fair Value, Inputs, Level 1 [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Fair value of asset	3,255	2,869
Fair Value, Inputs, Level 1 [Member] \| Equity Securities [Member] \| Common Stock [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, equity securities	175	149
Fair Value, Inputs, Level 1 [Member] \| Equity Securities [Member] \| Preferred Stock [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, equity securities		4
Fair Value, Inputs, Level 1 [Member] \| Fixed Maturities And Equity Securities [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Fair value of asset	175	153
Fair Value, Inputs, Level 2 [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Fair value of asset	9,904	9,477
Fair Value, Inputs, Level 2 [Member] \| Fixed Maturities [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, debt Securities	60	59
Fair Value, Inputs, Level 2 [Member] \| Fixed Maturities [Member] \| Corporate Fixed Maturities [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, debt Securities	24	25
Fair Value, Inputs, Level 2 [Member] \| Fixed Maturities [Member] \| States, Municipalities And Political Subdivisions [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, debt Securities	36	34
Fair Value, Inputs, Level 2 [Member] \| Fixed Maturities And Equity Securities [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Fair value of asset	60	59
Fair Value, Inputs, Level 3 [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Fair value of asset	5	25
Cincinnati Financial Corporation [Member]
Schedule of Pension and Other Postretirment Plan Assets by Fair Value [Line Items]
Available for sale securities, debt Securities	103	225
Available for sale securities, equity securities	$ 958	$ 806

Amount of debt securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

Amount of equity securities categorized neither as held-to-maturity nor as trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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+ Details

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investment securities as of the balance sheet date which may include marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References+ Details