v2.4.1.9

Summary Of Significant Accounting Policies (Health Insurer Fee) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
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Dec. 31, 2014
Health Insurer Fee [Abstract] |
Risk Adjustment Payable | $ 44 cnc_RiskAdjustmentPayable
Minimum medical loss ratio payable | 6 cnc_Minimummedicallossratiopayable
Reinsurance reimbursement threshold | ($45,000 with 80% coinsurance)
Reinsurance Receivables | 11 us-gaap_ReinsuranceReceivablesPaidLossesRecoverable
Risk Corridor Payable | $ 9 cnc_RiskCorridorPayable

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- Details
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- Definition Minimum medical loss ratio payable + References No definition available. + Details
Name: | cnc_Minimummedicallossratiopayable
Namespace Prefix: | cnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Reinsurance reimbursement threshold + References No definition available. + Details
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Namespace Prefix: | cnc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Risk Adjustment Payable + References No definition available. + Details
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Balance Type: | credit
Period Type: | instant

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- Definition Risk Corridor Payable + References No definition available. + Details
Name: | cnc_RiskCorridorPayable
Namespace Prefix: | cnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount after valuation allowance currently billed or billable under reinsurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6485522&loc=d3e21412-158489 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6485522&loc=d3e21409-158489 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.6) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 6 -Article 7 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
Name: | us-gaap_ReinsuranceReceivablesPaidLossesRecoverable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant