v2.4.1.9

Fair Value Measurements (Narrative) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Fair Value Disclosures [Abstract] |  |
Transfers from Level I to Level II | $ 14 us-gaap_FairValueAssetsLevel1ToLevel2TransfersAmount |
Transfers from Level II to Level I | 1 us-gaap_FairValueAssetsLevel2ToLevel1TransfersAmount |
Life insurance contracts and cost-method investments | $ 84 cnc_LifeInsuranceContractsAndCostMethodInvestmentsFairValueDisclosure | $ 37 cnc_LifeInsuranceContractsAndCostMethodInvestmentsFairValueDisclosure

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- Definition Life insurance contracts and cost method investments fair value disclosure + References No definition available. + Details
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Namespace Prefix: | cnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueAssetsLevel2ToLevel1TransfersAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration