v2.4.1.9

Short-Term And Long-Term Investments And Restricted Deposits (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 positions
Investments, Debt and Equity Securities [Abstract] |
Percentage of investments in securities recorded at fair value that carry a rating by S&P or Moody's of AAA/Aaa | 50.00%cnc_PercentageOfInvestmentsRecordedAtFairValueThatCarryRatingOfAaaOrAaa
Percentage of investments in securities recorded at fair value that carry a rating by S&P or Moody's of AA-/Aa3 or higher | 62.00%cnc_PercentageOfInvestmentsRecordedAtFairValueThatCarryRatingOfAaMinusOrAa3OrHigher
Percentage of investments in securities recorded at fair value that carry a rating by S&P or Moody's of A-/A3 or higher | 90.00%cnc_PercentageOfInvestmentsRecordedAtFairValueThatCarryRatingOfMinusOrA3OrHigher
Positions from which gross unrealized losses were generated | 116 cnc_PositionsFromWhichGrossUnrealizedLossesWereGenerated
Total number of positions | 341 cnc_Totalunrealizedinvestmentpositions
Income (Loss) from Equity Method Investments | $ 6 us-gaap_IncomeLossFromEquityMethodInvestments

X
- Definition The percentage of investments in securities recorded at fair value that carry a rating by Moody's or S&P of AAA/Aaa. + References No definition available. + Details
Name: | cnc_PercentageOfInvestmentsRecordedAtFairValueThatCarryRatingOfAaaOrAaa
Namespace Prefix: | cnc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The percentage of investments in securities recorded at fair value that carry a rating by Moody's or S&P of AA-/Aa3 or higher. + References No definition available. + Details
Name: | cnc_PercentageOfInvestmentsRecordedAtFairValueThatCarryRatingOfAaMinusOrAa3OrHigher
Namespace Prefix: | cnc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The percentage of investments in securities recorded at fair value that carry a rating by Moody's or S&P of A-/A3 or higher. + References No definition available. + Details
Name: | cnc_PercentageOfInvestmentsRecordedAtFairValueThatCarryRatingOfMinusOrA3OrHigher
Namespace Prefix: | cnc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Positions from which gross unrealized losses were generated + References No definition available. + Details
Name: | cnc_PositionsFromWhichGrossUnrealizedLossesWereGenerated
Namespace Prefix: | cnc_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Total Unrealized Investment Positions + References No definition available. + Details
Name: | cnc_Totalunrealizedinvestmentpositions
Namespace Prefix: | cnc_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35755396&loc=d3e33749-111570 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.12) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 11 -Article 7 + Details
Name: | us-gaap_IncomeLossFromEquityMethodInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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