v2.4.1.9

Discontinued Operations Discontinued Operations (Assets & Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets of Disposal Group, Including Discontinued Operation, Current	$ 75us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent	$ 78us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent
Disposal Group, Including Discontinued Operations, Long Term Investments and Restricted Deposits	25cnc_DisposalGroupIncludingDiscontinuedOperationsLongTermInvestmentsandRestrictedDeposits	38cnc_DisposalGroupIncludingDiscontinuedOperationsLongTermInvestmentsandRestrictedDeposits
Disposal Group, Including Discontinued Operation, Other Noncurrent Assets	0us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentAssets	0us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentAssets
Assets of Disposal Group, Including Discontinued Operation	100us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation	116us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation
Disposal Group, Including Discontinued Operations, Medical Claims Liability	10cnc_DisposalGroupIncludingDiscontinuedOperationsMedicalClaimsLiability	27cnc_DisposalGroupIncludingDiscontinuedOperationsMedicalClaimsLiability
Disposal Group, Including Discontinued Operation, Accounts Payable and Accrued Liabilities	7us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayableAndAccruedLiabilities	3us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayableAndAccruedLiabilities
Disposal Group, Including Discontinued Operation, Other Noncurrent Liabilities	1us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities	1us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities
Liabilities of discontinued operations	$ 18us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation	$ 31us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation

X

- Definition

Disposal Group, Including Discontinued Operations, Long Term Investments and Restricted Deposits

+ References

No definition available.

+ Details

Name:	cnc_DisposalGroupIncludingDiscontinuedOperationsLongTermInvestmentsandRestrictedDeposits
Namespace Prefix:	cnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Disposal Group, Including Discontinued Operations, Medical Claims Liability

+ References

No definition available.

+ Details

Name:	cnc_DisposalGroupIncludingDiscontinuedOperationsMedicalClaimsLiability
Namespace Prefix:	cnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount classified as assets attributable to disposal group held for sale or disposed of.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1107-107759

+ Details

Name:	us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount classified as assets attributable to disposal group held for sale or disposed of, expected to be disposed of within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1107-107759

+ Details

Name:	us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount classified as accounts payable and accrued liabilities attributable to disposal group held for sale or disposed of.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

+ Details

Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsPayableAndAccruedLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount classified as other assets attributable to disposal group held for sale or disposed of, expected to be disposed of after one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

+ Details

Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount classified as other liabilities attributable to disposal group held for sale or disposed of, expected to be disposed of beyond one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

+ Details

Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount classified as liabilities attributable to disposal group held for sale or disposed of.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1107-107759



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1436-107760

+ Details

Name:	us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant