v2.4.1.9

Short-Term And Long-Term Investments And Restricted Deposits (Short-Term And Long-Term Investments And Restricted Deposits By Investment Type) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | $ 1,556 us-gaap_AvailableForSaleSecuritiesAmortizedCost | $ 946 us-gaap_AvailableForSaleSecuritiesAmortizedCost
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 5 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax | 3 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | (4)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax | (8)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Fair Value | 1,557 us-gaap_AvailableForSaleSecurities | 941 us-gaap_AvailableForSaleSecurities
U.S. Treasury Securities And Obligations Of U.S. Government Corporations And Agencies [Member] |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 393 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_USTreasuryAndGovernmentMember | 246 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_USTreasuryAndGovernmentMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 1 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_USTreasuryAndGovernmentMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_USTreasuryAndGovernmentMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | (2)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_USTreasuryAndGovernmentMember | (7)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_USTreasuryAndGovernmentMember
Fair Value | 392 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_USTreasuryAndGovernmentMember | 239 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_USTreasuryAndGovernmentMember
Corporate Securities [Member] |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 556 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_CorporateDebtSecuritiesMember | 294 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_CorporateDebtSecuritiesMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 2 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_CorporateDebtSecuritiesMember | 3 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_CorporateDebtSecuritiesMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | (2)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_CorporateDebtSecuritiesMember | (1)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_CorporateDebtSecuritiesMember
Fair Value | 556 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_CorporateDebtSecuritiesMember | 296 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_CorporateDebtSecuritiesMember
Restricted Certificates Of Deposit [Member] |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 6 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCertificatesOfDepositMember | 6 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCertificatesOfDepositMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCertificatesOfDepositMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCertificatesOfDepositMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCertificatesOfDepositMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCertificatesOfDepositMember
Fair Value | 6 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCertificatesOfDepositMember | 6 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCertificatesOfDepositMember
Restricted Cash Equivalents [Member] |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 79 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCashEquivalentsMember | 27 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCashEquivalentsMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCashEquivalentsMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCashEquivalentsMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCashEquivalentsMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCashEquivalentsMember
Fair Value | 79 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCashEquivalentsMember | 27 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_RestrictedCashEquivalentsMember
Municipal Securities, General Obligation [Member] |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 54 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MunicipalBondsMember | 54 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MunicipalBondsMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MunicipalBondsMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MunicipalBondsMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MunicipalBondsMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MunicipalBondsMember
Fair Value | 54 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MunicipalBondsMember | 54 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MunicipalBondsMember
Municipal Securities, Pre Refunded [Member] |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 5 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesPreRefundedMember | 11 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesPreRefundedMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesPreRefundedMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesPreRefundedMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesPreRefundedMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesPreRefundedMember
Fair Value | 5 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesPreRefundedMember | 11 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesPreRefundedMember
Municipal Securities, Revenue [Member] |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 101 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesRevenueMember | 69 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesRevenueMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 1 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesRevenueMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesRevenueMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesRevenueMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesRevenueMember
Fair Value | 102 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesRevenueMember | 69 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_MunicipalSecuritiesRevenueMember
Municipal Securities, Variable Rate Demand Notes [Member] |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 14 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_VariableRateDemandObligationMember | 29 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_VariableRateDemandObligationMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_VariableRateDemandObligationMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_VariableRateDemandObligationMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_VariableRateDemandObligationMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_VariableRateDemandObligationMember
Fair Value | 14 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_VariableRateDemandObligationMember | 29 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_VariableRateDemandObligationMember
Asset Backed Securities [Member] |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 180 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_AssetBackedSecuritiesMember | 139 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_AssetBackedSecuritiesMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_AssetBackedSecuritiesMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_AssetBackedSecuritiesMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_AssetBackedSecuritiesMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_AssetBackedSecuritiesMember
Fair Value | 180 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_AssetBackedSecuritiesMember | 139 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_AssetBackedSecuritiesMember
Mortgage backed securities |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 84 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember | 34 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 1 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Fair Value | 85 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember | 34 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Cost And Equity Method Investments [Member] |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 68 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_CostMethodInvestmentsAndEquityMethodSecuritiesMember | 22 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_CostMethodInvestmentsAndEquityMethodSecuritiesMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_CostMethodInvestmentsAndEquityMethodSecuritiesMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_CostMethodInvestmentsAndEquityMethodSecuritiesMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_CostMethodInvestmentsAndEquityMethodSecuritiesMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_CostMethodInvestmentsAndEquityMethodSecuritiesMember
Fair Value | 68 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_CostMethodInvestmentsAndEquityMethodSecuritiesMember | 22 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_CostMethodInvestmentsAndEquityMethodSecuritiesMember
Life Insurance Contracts [Member] |  |
Schedule Of Investments And Restricted Deposits By Type [Line Items] |  |
Amortized Cost | 16 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_LifeInsuranceContractsMember | 15 us-gaap_AvailableForSaleSecuritiesAmortizedCost / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_LifeInsuranceContractsMember
Available For Sale Securities Gross Unrealized Gain Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_LifeInsuranceContractsMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_LifeInsuranceContractsMember
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_LifeInsuranceContractsMember | 0 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_LifeInsuranceContractsMember
Fair Value | $ 16 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_LifeInsuranceContractsMember | $ 15 us-gaap_AvailableForSaleSecurities / cnc_ScheduleOfInvestmentsAndRestrictedDepositsByTypeAxis = cnc_LifeInsuranceContractsMember

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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563 + Details
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- Definition Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563 + Details
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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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