Number of Industries Operated In

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Number of Insurance Segments

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Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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- Definition

Amount of fees and commissions from financial services and banking activities and correspondent clearing. Includes fees from depositor accounts, credit cards, merchant discounts, and fiduciary and trust activities, guarantee fees, investment advisory, management, and administrative fees, transfer agent fees, and insurance commissions.

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

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Reflects the sum of all other revenue and income recognized by the entity in the period not otherwise specified in the income statement.

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Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 industry segment	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information
Earned premiums									$ 4,243us-gaap_PremiumsEarnedNet	$ 3,902us-gaap_PremiumsEarnedNet	$ 3,522us-gaap_PremiumsEarnedNet
Revenues	1,262us-gaap_Revenues	1,280us-gaap_Revenues	1,214us-gaap_Revenues	1,189us-gaap_Revenues	1,172us-gaap_Revenues	1,152us-gaap_Revenues	1,104us-gaap_Revenues	1,103us-gaap_Revenues	4,945us-gaap_Revenues	4,531us-gaap_Revenues	4,111us-gaap_Revenues
Other Income									8us-gaap_OtherIncome	9us-gaap_OtherIncome	10us-gaap_OtherIncome
Fees and Commissions									12us-gaap_FeesAndCommissions	8us-gaap_FeesAndCommissions	6us-gaap_FeesAndCommissions
Net Investment Income									549us-gaap_NetInvestmentIncome	529us-gaap_NetInvestmentIncome	531us-gaap_NetInvestmentIncome
Realized investment gains, net									133us-gaap_RealizedInvestmentGainsLosses	83us-gaap_RealizedInvestmentGainsLosses	42us-gaap_RealizedInvestmentGainsLosses
Income before income taxes	236	259	107	119	167	182	148	217	721	714	566
Identifiable assets	18,753us-gaap_Assets				17,662us-gaap_Assets				18,753us-gaap_Assets	17,662us-gaap_Assets
Number of Industries Operated In									2cinf_NumberofIndustriesOperatedIn
Number of Insurance Segments									4cinf_NumberofInsuranceSegments
Life Insurance Segment
Segment Reporting Information
Earned premiums									198	189	178
Identifiable assets	1,316				1,225				1,316	1,225
Investments Segment
Segment Reporting Information
Identifiable assets	14,441				13,618				14,441	13,618
Consolidated Property and Casualty Insurance Entity
Segment Reporting Information
Identifiable assets	2,656				2,455				2,656	2,455
Corporate and Other Non-Segment
Segment Reporting Information
Other Income									8	9	9
Income before income taxes									(59)	(60)	(59)
Identifiable assets	340				364				340	364
Operating Segments \| Commercial Insurance
Segment Reporting Information
Earned premiums									2,856	2,636	2,383
Revenues									2,860	2,639	2,387
Fees and Commissions									4	3	4
Income before income taxes									146	186	181
Operating Segments \| Commercial Insurance \| Commercial Casualty Line
Segment Reporting Information
Earned premiums									938	856	767
Operating Segments \| Commercial Insurance \| Commercial Property Line
Segment Reporting Information
Earned premiums									728	623	545
Operating Segments \| Commercial Insurance \| Commercial Auto Line
Segment Reporting Information
Earned premiums									528	479	426
Operating Segments \| Commercial Insurance \| Workers' Compensation Line
Segment Reporting Information
Earned premiums									370	365	344
Operating Segments \| Commercial Insurance \| Other Commercial Lines
Segment Reporting Information
Earned premiums									292	313	301
Operating Segments \| Personal Insurance
Segment Reporting Information
Earned premiums									1,041	961	868
Revenues									1,043	962	870
Fees and Commissions									2	1	2
Income before income taxes									10	33	(43)
Operating Segments \| Personal Insurance \| Personal Auto
Segment Reporting Information
Earned premiums									476	443	404
Operating Segments \| Personal Insurance \| Home Owner Line
Segment Reporting Information
Earned premiums									443	403	353
Operating Segments \| Personal Insurance \| Other Personal Lines
Segment Reporting Information
Earned premiums									122	115	111
Operating Segments \| Excess and Surplus Lines Insurance
Segment Reporting Information
Earned premiums									148	116	93
Income before income taxes									30	14	(1)
Operating Segments \| Life Insurance Segment
Segment Reporting Information
Earned premiums									198	189	178
Revenues									204	193	179
Fees and Commissions									6	4	1
Income before income taxes									(5)	9	(3)
Operating Segments \| Investments Segment
Segment Reporting Information
Revenues									682	612	573
Net Investment Income									549	529	531
Realized investment gains, net									133	83	42
Income before income taxes									$ 599	$ 532	$ 491