v2.4.1.9

Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013
Income Taxes [Line Items] |  |
Unrecognized Tax Benefits | $ 4 us-gaap_UnrecognizedTaxBenefits | $ 3 us-gaap_UnrecognizedTaxBenefits
Federal and state net operating losses acquired in business combinations | 5 cnc_NetOperatingLossesAcquiredInBusinessCombinations |
Valuation allowance additions in the tax provision | 5 cnc_ValuationAllowanceAdditions | 1 cnc_ValuationAllowanceAdditions
Valuation allowance reductions | 1 cnc_ValuationAllowanceReductions | 1 cnc_ValuationAllowanceReductions
Tax Benefit Related to 2013 | $ 14 cnc_TaxBenefitRelatedto2013 |
Minimum [Member] |  |
Income Taxes [Line Items] |  |
Federal Net Operating Losses Expire Period | 2020 |
State Net Operating Losses Expire Period | 2015 |
Maximum [Member] |  |
Income Taxes [Line Items] |  |
Federal Net Operating Losses Expire Period | 2033 |
State Net Operating Losses Expire Period | 2035 |

X
- Definition Federal net operating losses expire period. + References No definition available. + Details
Name: | cnc_FederalNetOperatingLossesExpirePeriod
Namespace Prefix: | cnc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | cnc_IncomeTaxesLineItems
Namespace Prefix: | cnc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Net Operating Losses Acquired In Business Combinations + References No definition available. + Details
Name: | cnc_NetOperatingLossesAcquiredInBusinessCombinations
Namespace Prefix: | cnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition State net operating losses expire period. + References No definition available. + Details
Name: | cnc_StateNetOperatingLossesExpirePeriod
Namespace Prefix: | cnc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tax benefit recognized for new regulations on compensation deduction limitation in 2013 and 2014, related to 2013. + References No definition available. + Details
Name: | cnc_TaxBenefitRelatedto2013
Namespace Prefix: | cnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Valuation allowance additions. + References No definition available. + Details
Name: | cnc_ValuationAllowanceAdditions
Namespace Prefix: | cnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Valuation allowance reductions. + References No definition available. + Details
Name: | cnc_ValuationAllowanceReductions
Namespace Prefix: | cnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Unrecognized Tax Benefit -URI http://asc.fasb.org/extlink&oid=6527854 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |