v2.4.1.9
Debt (Narrative) (Details)
In Millions, unless otherwise specified
3 Months Ended 1 Months Ended 12 Months Ended
Dec. 31, 2014
USD ($)
Apr. 30, 2014
USD ($)
Dec. 31, 2013
USD ($)
May 31, 2013
USD ($)
May 31, 2011
USD ($)
Apr. 30, 2014
Four Point Seven Five Percent Senior Notes [Member]
USD ($)
May 31, 2011
Five Point Seven Five Percent Senior Notes [Member]
USD ($)
Dec. 31, 2014
Non-recourse Mortgage Note Due January 1, 2021 [Member]
USD ($)
Dec. 31, 2014
Ribera Salud [Member]
USD ($)
Dec. 31, 2014
Ribera Salud [Member]
EUR (€)
Dec. 31, 2014
Non Revolver Letter of Credit [Member]
USD ($)
Dec. 31, 2014
Interest Rate Swap [Member]
USD ($)
Debt Instrument [Line Items]                        
Line of Credit Facility, Covenant Terms The agreement contains non-financial and financial covenants, including requirements of minimum fixed charge coverage ratios, maximum debt-to-EBITDA ratios and minimum tangible net worth. The Company is required to not exceed a maximum debt-to-EBITDA ratio of 3.0 to 1.0.                      
Mortgage notes payable $ 70us-gaap_OtherNotesPayable   $ 73us-gaap_OtherNotesPayable                  
Line of Credit Facility, Current Borrowing Capacity 500us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity                      
Senior notes, at par 429cnc_SeniorNotesAtPar   431cnc_SeniorNotesAtPar     300cnc_SeniorNotesAtPar
/ us-gaap_LongtermDebtTypeAxis
= cnc_FourPointSevenFivePercentSeniorNotesMember
425cnc_SeniorNotesAtPar
/ us-gaap_LongtermDebtTypeAxis
= cnc_FivePointSevenFivePercentSeniorNotesMember
         
Derivative, Notional Amount   300invest_DerivativeNotionalAmount     250invest_DerivativeNotionalAmount             550invest_DerivativeNotionalAmount
/ us-gaap_VariableRateAxis
= us-gaap_InterestRateSwapMember
Interest rate on notes, percentage           4.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= cnc_FourPointSevenFivePercentSeniorNotesMember
5.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= cnc_FivePointSevenFivePercentSeniorNotesMember
         
Debt Instrument, Maturity Date           May 15, 2022 Jun. 01, 2017 Jan. 01, 2021        
Senior notes, effective yield 1.73%us-gaap_DebtInstrumentInterestRateEffectivePercentage                      
Debt Instrument, Unamortized Premium 300us-gaap_DebtInstrumentUnamortizedPremium   0us-gaap_DebtInstrumentUnamortizedPremium                  
Fair value of swap agreements 11us-gaap_InterestRateDerivativeAssetsAtFairValue   10us-gaap_InterestRateDerivativeAssetsAtFairValue                  
Variable rate of swap, percentage                       2.83%us-gaap_DerivativeVariableInterestRate
/ us-gaap_VariableRateAxis
= us-gaap_InterestRateSwapMember
weighted average interest rate, interest rate swap agreements                       3.06%cnc_Weightedaverageinterestrateinterestrateswapagreements
/ us-gaap_VariableRateAxis
= us-gaap_InterestRateSwapMember
Revolving credit facility, maximum borrowing capacity       500us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity                
Revolving credit facility, due date Jun. 01, 2018                      
Line of Credit, Minimum carrying amount of unrestricted cash 100cnc_LineofCreditMinimumcarryingamountofunrestrictedcash                      
Line of Credit Facility, Amount Outstanding 75us-gaap_LineOfCredit   150us-gaap_LineOfCredit                  
Letters of Credit Outstanding, Amount                 58us-gaap_LettersOfCreditOutstandingAmount
/ dei_LegalEntityAxis
= cnc_RiberaSaludMember
48us-gaap_LettersOfCreditOutstandingAmount
/ dei_LegalEntityAxis
= cnc_RiberaSaludMember
30us-gaap_LettersOfCreditOutstandingAmount
/ us-gaap_CreditFacilityAxis
= cnc_NonRevolverLetterofCreditMember
 
Mortgage note non-recourse interest rate               5.14%us-gaap_MortgageLoansOnRealEstateInterestRate
/ us-gaap_LongtermDebtTypeAxis
= cnc_NonRecourseMortgageNoteDueJanuary12021Member
       
Net Book Value Of Collateralized Properties               159cnc_NetBookValueOfCollateralizedProperties
/ us-gaap_LongtermDebtTypeAxis
= cnc_NonRecourseMortgageNoteDueJanuary12021Member
       
Weighted average interest rate of outstanding borrowings 1.91%us-gaap_DebtWeightedAverageInterestRate                      
Surety Bonds 142us-gaap_GuaranteeObligationsMaximumExposure                      
Fair value of outstanding debt $ 901us-gaap_LongTermDebtFairValue   $ 673us-gaap_LongTermDebtFairValue