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Fair Value Measurements - Measured Under Certain Conditions (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Financing Receivable, Impaired [Line Items]    
Realized investment losses on impaired commercial mortgage loans and real estate entities $ 4ci_RealizedInvestmentLossesCommercialMortgageLoansAndRealEstateEntities $ 4ci_RealizedInvestmentLossesCommercialMortgageLoansAndRealEstateEntities
Maximum [Member]    
Financing Receivable, Impaired [Line Items]    
Impaired commercial mortgage loans and real estate entities as a percent of total investments 1.00%ci_PercentageOfImpairedCommercialMortgageLoansAndRealEstateEntitiesOfTotalInvestments
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 1.00%ci_PercentageOfImpairedCommercialMortgageLoansAndRealEstateEntitiesOfTotalInvestments
/ us-gaap_RangeAxis
= us-gaap_MaximumMember