v2.4.1.9

Property, Software And Equipment (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property, software and equipment, gross	$ 733us-gaap_PropertyPlantAndEquipmentGross	$ 639us-gaap_PropertyPlantAndEquipmentGross
Less accumulated depreciation	(288)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	(244)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
Property, software and equipment, net	445us-gaap_PropertyPlantAndEquipmentNet	395us-gaap_PropertyPlantAndEquipmentNet
Depreciation expense	65us-gaap_Depreciation	52us-gaap_Depreciation	49us-gaap_Depreciation
Computer Software [Member]
Property, Plant and Equipment [Line Items]
Property, software and equipment, gross	198us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_ComputerSoftwareIntangibleAssetMember	185us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_ComputerSoftwareIntangibleAssetMember
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, software and equipment, gross	208us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_BuildingMember	206us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_BuildingMember
Land [Member]
Property, Plant and Equipment [Line Items]
Property, software and equipment, gross	87us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandMember	69us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandMember
Computer Hardware [Member]
Property, Plant and Equipment [Line Items]
Property, software and equipment, gross	88us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cnc_ComputerHardwareMember	69us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cnc_ComputerHardwareMember
Furniture And Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, software and equipment, gross	70us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cnc_FurnitureAndOfficeEquipmentMember	53us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cnc_FurnitureAndOfficeEquipmentMember
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, software and equipment, gross	82us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LeaseholdImprovementsMember	57us-gaap_PropertyPlantAndEquipmentGross / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LeaseholdImprovementsMember
Assets Held Under Capital Leases [Member]
Property, Plant and Equipment [Line Items]
Less accumulated depreciation	(3)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_AssetsHeldUnderCapitalLeasesMember	(2)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_AssetsHeldUnderCapitalLeasesMember
Property, software and equipment, net	$ 7us-gaap_PropertyPlantAndEquipmentNet / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_AssetsHeldUnderCapitalLeasesMember	$ 6us-gaap_PropertyPlantAndEquipmentNet / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_AssetsHeldUnderCapitalLeasesMember

X

- Definition

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.14)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 14

-Article 5

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- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

+ 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

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- Definition

Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.13)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.13)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 13

-Subparagraph a

-Article 5



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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