v3.8.0.1

Summary of Significant Accounting Policies - Significant Customers (Details) | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
California |  |  |
Segment Reporting Information [Line Items] |  |  |
Percentage of revenues under contracts or subcontracts | 18.00% | 21.00% | 3.00%
Florida |  |  |
Segment Reporting Information [Line Items] |  |  |
Percentage of revenues under contracts or subcontracts |  |  | 14.00%
Texas |  |  |
Segment Reporting Information [Line Items] |  |  |
Percentage of revenues under contracts or subcontracts | 12.00% | 13.00% | 22.00%

X
- Definition Percentage of revenues under contracts or subcontracts. + References No definition available. + Details
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Namespace Prefix: | cnc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=stpr_FL
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=stpr_TX
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |