v2.4.1.9
Condensed Financial Information Of Registrant (Condensed Statements Of Operations) (Details) (USD $)
In Millions, except Share data, 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
Dec. 31, 2013
Dec. 31, 2012
General and administrative expenses                 $ 1,314us-gaap_GeneralAndAdministrativeExpense $ 931us-gaap_GeneralAndAdministrativeExpense $ 677us-gaap_GeneralAndAdministrativeExpense
Investment and other income                 28us-gaap_InvestmentIncomeNonoperating 19us-gaap_InvestmentIncomeNonoperating 35us-gaap_InvestmentIncomeNonoperating
Interest Expense                 (35)us-gaap_InterestExpense (27)us-gaap_InterestExpense (20)us-gaap_InterestExpense
Earnings (loss) before income taxes                 457us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments 269us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments 123us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Income tax expense                 196us-gaap_IncomeTaxExpenseBenefit 107us-gaap_IncomeTaxExpenseBenefit 47us-gaap_IncomeTaxExpenseBenefit
Equity in earnings from subsidiaries                 6us-gaap_IncomeLossFromEquityMethodInvestments    
Net earnings (loss) before equity in subsidiaries                 264us-gaap_ProfitLoss 166us-gaap_ProfitLoss (11)us-gaap_ProfitLoss
Net Income (Loss) Attributable to Noncontrolling Interest                 7us-gaap_NetIncomeLossAttributableToNoncontrollingInterest (1)us-gaap_NetIncomeLossAttributableToNoncontrollingInterest 13us-gaap_NetIncomeLossAttributableToNoncontrollingInterest
Income (Loss) from Continuing Operations Attributable to Parent 106us-gaap_IncomeLossFromContinuingOperations 81us-gaap_IncomeLossFromContinuingOperations 47us-gaap_IncomeLossFromContinuingOperations 34us-gaap_IncomeLossFromContinuingOperations 48us-gaap_IncomeLossFromContinuingOperations 50us-gaap_IncomeLossFromContinuingOperations 41us-gaap_IncomeLossFromContinuingOperations 23us-gaap_IncomeLossFromContinuingOperations 268us-gaap_IncomeLossFromContinuingOperations 161us-gaap_IncomeLossFromContinuingOperations 89us-gaap_IncomeLossFromContinuingOperations
Basic earnings (loss) per common share (in dollars per share) $ 0.91us-gaap_EarningsPerShareBasic $ 0.70us-gaap_EarningsPerShareBasic $ 0.42us-gaap_EarningsPerShareBasic $ 0.29us-gaap_EarningsPerShareBasic $ 0.48us-gaap_EarningsPerShareBasic $ 0.45us-gaap_EarningsPerShareBasic $ 0.37us-gaap_EarningsPerShareBasic $ 0.22us-gaap_EarningsPerShareBasic $ 2.33us-gaap_EarningsPerShareBasic $ 1.52us-gaap_EarningsPerShareBasic $ 0.02us-gaap_EarningsPerShareBasic
Diluted earnings (loss) per common share (in dollars per share) $ 0.88us-gaap_EarningsPerShareDiluted $ 0.68us-gaap_EarningsPerShareDiluted $ 0.41us-gaap_EarningsPerShareDiluted $ 0.28us-gaap_EarningsPerShareDiluted $ 0.46us-gaap_EarningsPerShareDiluted $ 0.43us-gaap_EarningsPerShareDiluted $ 0.35us-gaap_EarningsPerShareDiluted $ 0.21us-gaap_EarningsPerShareDiluted $ 2.25us-gaap_EarningsPerShareDiluted $ 1.47us-gaap_EarningsPerShareDiluted $ 0.02us-gaap_EarningsPerShareDiluted
Basic                 116,345,764us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 108,253,090us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 103,018,732us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
Diluted                 120,360,212us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 112,494,346us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 107,428,750us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
Parent Company [Member]                      
General and administrative expenses                 3us-gaap_GeneralAndAdministrativeExpense
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
4us-gaap_GeneralAndAdministrativeExpense
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
4us-gaap_GeneralAndAdministrativeExpense
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Investment and other income                 1us-gaap_InvestmentIncomeNonoperating
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1us-gaap_InvestmentIncomeNonoperating
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
20us-gaap_InvestmentIncomeNonoperating
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Interest Expense                 (30)us-gaap_InterestExpense
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(23)us-gaap_InterestExpense
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(16)us-gaap_InterestExpense
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Earnings (loss) before income taxes                 (32)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(26)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Income tax expense                 (8)us-gaap_IncomeTaxExpenseBenefit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(15)us-gaap_IncomeTaxExpenseBenefit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(10)us-gaap_IncomeTaxExpenseBenefit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
net income (loss), including portion attributable to noncontrolling interest before equity in earnings from subsidiaries                 (24)cnc_Netincomelossincludingportionattributabletononcontrollinginterestbeforeequityinearningsfromsubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(11)cnc_Netincomelossincludingportionattributabletononcontrollinginterestbeforeequityinearningsfromsubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
10cnc_Netincomelossincludingportionattributabletononcontrollinginterestbeforeequityinearningsfromsubsidiaries
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Equity in earnings from subsidiaries                 285us-gaap_IncomeLossFromEquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
173us-gaap_IncomeLossFromEquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
66us-gaap_IncomeLossFromEquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Net earnings (loss) before equity in subsidiaries                 261us-gaap_ProfitLoss
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
162us-gaap_ProfitLoss
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
76us-gaap_ProfitLoss
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Net Income (Loss) Attributable to Noncontrolling Interest                 7us-gaap_NetIncomeLossAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(1)us-gaap_NetIncomeLossAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
13us-gaap_NetIncomeLossAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Income (Loss) from Continuing Operations Attributable to Parent                 $ 268us-gaap_IncomeLossFromContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
$ 161us-gaap_IncomeLossFromContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
$ 89us-gaap_IncomeLossFromContinuingOperations
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Basic earnings (loss) per common share (in dollars per share)                 $ 2.30us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
$ 1.49us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
$ 0.86us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Diluted earnings (loss) per common share (in dollars per share)                 $ 2.23us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
$ 1.43us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
$ 0.83us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Basic                 116,345,764us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
108,253,090us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
103,018,732us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Diluted                 120,360,212us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
112,494,346us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
107,428,750us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember