Summary of Investments Other Than Investments In Related Parties (Details)1 (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	$ 11,229
Balance sheet	13,564
Fixed Maturities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	8,638
Fair value	9,121
Balance sheet	9,121
Equity Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	2,523
Fair value	4,375
Balance sheet	4,375
Other than Securities Investment [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	68
Balance sheet	68
States, Municipalities And Political Subdivisions [Member] | Fixed Maturities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	3,107
Fair value	3,211
Balance sheet	3,211
States, Municipalities And Political Subdivisions [Member] | Fixed Maturities [Member] | Cincinnati Casualty Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	122
Fair value	127
Balance sheet	127
States, Municipalities And Political Subdivisions [Member] | Fixed Maturities [Member] | Cincinnati Indemnity Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	32
Fair value	33
Balance sheet	33
States, Municipalities And Political Subdivisions [Member] | Fixed Maturities [Member] | Cincinnati Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	2,569
Fair value	2,648
Balance sheet	2,648
States, Municipalities And Political Subdivisions [Member] | Fixed Maturities [Member] | Cincinnati Life Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	1
Fair value	1
Balance sheet	1
States, Municipalities And Political Subdivisions [Member] | Fixed Maturities [Member] | CSU Producers Resources Inc. [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	190
Fair value	197
Balance sheet	197
States, Municipalities And Political Subdivisions [Member] | Fixed Maturities [Member] | Cincinnati Specialty Underwriters Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	193
Fair value	205
Balance sheet	205
Convertibles And Bonds With Warrants Attached [Member] | Fixed Maturities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	17
Fair value	17
Balance sheet	17
Convertibles And Bonds With Warrants Attached [Member] | Fixed Maturities [Member] | Cincinnati Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	17
Fair value	17
Balance sheet	17
United States Government [Member] | Fixed Maturities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	7
Fair value	7
Balance sheet	7
United States Government [Member] | Fixed Maturities [Member] | Cincinnati Casualty Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	1
Fair value	1
Balance sheet	1
United States Government [Member] | Fixed Maturities [Member] | Cincinnati Indemnity Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	1
Fair value	1
Balance sheet	1
United States Government [Member] | Fixed Maturities [Member] | Cincinnati Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	1
Fair value	1
Balance sheet	1
United States Government [Member] | Fixed Maturities [Member] | Cincinnati Life Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	4
Fair value	4
Balance sheet	4
Government-Sponsored Enterprises [Member] | Fixed Maturities [Member] | Cincinnati Life Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	15
Fair value	14
Balance sheet	14
Foreign Government [Member] | Fixed Maturities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	10
Fair value	10
Balance sheet	10
Foreign Government [Member] | Fixed Maturities [Member] | Cincinnati Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	10
Fair value	10
Balance sheet	10
Common Stock [Member] | Equity Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	2,396
Fair value	4,213
Balance sheet	4,213
Common Stock [Member] | Equity Securities [Member] | Cincinnati Financial Corporation [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	847
Fair value	1,363
Balance sheet	1,363
Common Stock [Member] | Equity Securities [Member] | Cincinnati Casualty Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	47
Fair value	89
Balance sheet	89
Common Stock [Member] | Equity Securities [Member] | Cincinnati Indemnity Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	13
Fair value	22
Balance sheet	22
Common Stock [Member] | Equity Securities [Member] | Cincinnati Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	1,437
Fair value	2,659
Balance sheet	2,659
Common Stock [Member] | Equity Securities [Member] | CSU Producers Resources Inc. [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	4
Fair value	6
Balance sheet	6
Common Stock [Member] | Equity Securities [Member] | Cincinnati Specialty Underwriters Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	48
Fair value	74
Balance sheet	74
Nonredeemable Preferred Stock [Member] | Equity Securities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	127
Fair value	162
Balance sheet	162
Nonredeemable Preferred Stock [Member] | Equity Securities [Member] | Cincinnati Financial Corporation [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	3
Fair value	3
Balance sheet	3
Nonredeemable Preferred Stock [Member] | Equity Securities [Member] | Cincinnati Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	117
Fair value	146
Balance sheet	146
Nonredeemable Preferred Stock [Member] | Equity Securities [Member] | Cincinnati Life Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	7
Fair value	13
Balance sheet	13
All Other Corporate Bonds [Member] | Fixed Maturities [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	5,270
Fair value	5,676
Balance sheet	5,676
All Other Corporate Bonds [Member] | Fixed Maturities [Member] | Cincinnati Financial Corporation [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	61
Fair value	75
Balance sheet	75
All Other Corporate Bonds [Member] | Fixed Maturities [Member] | Cincinnati Casualty Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	114
Fair value	121
Balance sheet	121
All Other Corporate Bonds [Member] | Fixed Maturities [Member] | Cincinnati Indemnity Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	28
Fair value	29
Balance sheet	29
All Other Corporate Bonds [Member] | Fixed Maturities [Member] | Cincinnati Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	2,518
Fair value	2,726
Balance sheet	2,726
All Other Corporate Bonds [Member] | Fixed Maturities [Member] | Cincinnati Life Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	2,382
Fair value	2,551
Balance sheet	2,551
All Other Corporate Bonds [Member] | Fixed Maturities [Member] | CSU Producers Resources Inc. [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	5
Fair value	5
Balance sheet	5
All Other Corporate Bonds [Member] | Fixed Maturities [Member] | Cincinnati Specialty Underwriters Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	162
Fair value	169
Balance sheet	169
Policy Loans [Member] | Other than Securities Investment [Member] | Cincinnati Life Insurance Company [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	36
Balance sheet	36
Limited Partnership [Member] | Other than Securities Investment [Member] | Cincinnati Financial Corporation [Member]
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]
Cost or amortized cost	32
Balance sheet	$ 32