v2.4.1.9

Goodwill And Other Intangible Assets Goodwill and Intangible Assets, Test for Impairment (Details) | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2014 | Dec. 01, 2014 | Dec. 01, 2013 | Dec. 01, 2012
Goodwill [Line Items] |  |  |  |
Number of Reportable Segments | 2 us-gaap_NumberOfReportableSegments |  |  |
Number of operating segments which do not meet reporting unit quantitative threshold | 3 cdw_NumberOfOperatingSegmentsWhichDoNotMeetReportableUnitQuantitativeThreshold |  |  |
Goodwill Impairment Test, Income Approach Weight |  | 75.00%cdw_GoodwillImpairmentTestIncomeApproachWeight | 75.00%cdw_GoodwillImpairmentTestIncomeApproachWeight | 75.00%cdw_GoodwillImpairmentTestIncomeApproachWeight
Goodwill Impairment Test, Market Approach Weight |  | 25.00%cdw_GoodwillImpairmentTestMarketApproachWeight | 25.00%cdw_GoodwillImpairmentTestMarketApproachWeight | 25.00%cdw_GoodwillImpairmentTestMarketApproachWeight
Years Forecasted in Goodwill Impairment Income Approach |  | 6 cdw_YearsForecastedInGoodwillImpairmentIncomeApproach | 6 cdw_YearsForecastedInGoodwillImpairmentIncomeApproach | 6 cdw_YearsForecastedInGoodwillImpairmentIncomeApproach
Long-Term Consolidated Annual Growth Rate |  | 3.50%cdw_LongTermConsolidatedAnnualGrowthRate | 3.50%cdw_LongTermConsolidatedAnnualGrowthRate | 3.50%cdw_LongTermConsolidatedAnnualGrowthRate
Corporate Reporting Unit [Member] |  |  |  |
Goodwill [Line Items] |  |  |  |
Reporting unit fair value in excess of carrying value |  | 169.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / cdw_ReportingUnitsAxis = cdw_CorporateReportingUnitMember | 107.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / cdw_ReportingUnitsAxis = cdw_CorporateReportingUnitMember | 49.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / cdw_ReportingUnitsAxis = cdw_CorporateReportingUnitMember
Goodwill, Assumptions Used in Impairment Test, Discount Rate |  | 9.00%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / cdw_ReportingUnitsAxis = cdw_CorporateReportingUnitMember | 10.00%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / cdw_ReportingUnitsAxis = cdw_CorporateReportingUnitMember | 11.50%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / cdw_ReportingUnitsAxis = cdw_CorporateReportingUnitMember
Public Segment Reporting Unit [Member] |  |  |  |
Goodwill [Line Items] |  |  |  |
Reporting unit fair value in excess of carrying value |  | 147.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / cdw_ReportingUnitsAxis = cdw_PublicReportingUnitMember | 82.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / cdw_ReportingUnitsAxis = cdw_PublicReportingUnitMember | 44.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / cdw_ReportingUnitsAxis = cdw_PublicReportingUnitMember
Goodwill, Assumptions Used in Impairment Test, Discount Rate |  | 9.00%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / cdw_ReportingUnitsAxis = cdw_PublicReportingUnitMember | 10.00%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / cdw_ReportingUnitsAxis = cdw_PublicReportingUnitMember | 11.50%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / cdw_ReportingUnitsAxis = cdw_PublicReportingUnitMember
Canada Operating Segment [Member] |  |  |  |
Goodwill [Line Items] |  |  |  |
Reporting unit fair value in excess of carrying value |  | 276.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / us-gaap_StatementBusinessSegmentsAxis = cdw_CanadaOperatingSegmentMember | 167.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / us-gaap_StatementBusinessSegmentsAxis = cdw_CanadaOperatingSegmentMember | 104.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / us-gaap_StatementBusinessSegmentsAxis = cdw_CanadaOperatingSegmentMember
Goodwill, Assumptions Used in Impairment Test, Discount Rate |  | 9.30%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / us-gaap_StatementBusinessSegmentsAxis = cdw_CanadaOperatingSegmentMember | 10.30%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / us-gaap_StatementBusinessSegmentsAxis = cdw_CanadaOperatingSegmentMember | 11.80%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / us-gaap_StatementBusinessSegmentsAxis = cdw_CanadaOperatingSegmentMember
CDW Advanced Services Operating Segment [Member] |  |  |  |
Goodwill [Line Items] |  |  |  |
Reporting unit fair value in excess of carrying value |  | 78.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / us-gaap_StatementBusinessSegmentsAxis = cdw_CDWAdvancedServicesOperatingSegmentMember | 168.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / us-gaap_StatementBusinessSegmentsAxis = cdw_CDWAdvancedServicesOperatingSegmentMember | 17.00%cdw_ReportingUnitFairValueInExcessOfCarryingValue / us-gaap_StatementBusinessSegmentsAxis = cdw_CDWAdvancedServicesOperatingSegmentMember
Goodwill, Assumptions Used in Impairment Test, Discount Rate |  | 11.50%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / us-gaap_StatementBusinessSegmentsAxis = cdw_CDWAdvancedServicesOperatingSegmentMember | 10.50%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / us-gaap_StatementBusinessSegmentsAxis = cdw_CDWAdvancedServicesOperatingSegmentMember | 12.00%cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate / us-gaap_StatementBusinessSegmentsAxis = cdw_CDWAdvancedServicesOperatingSegmentMember

X
- Definition Discount rate used in the impairment test for Goodwill. + References No definition available. + Details
Name: | cdw_GoodwillAssumptionsUsedInImpairmentTestDiscountRate
Namespace Prefix: | cdw_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The weight provided to the Income Approach in determining the fair value of goodwill for a given reporting unit as part of the test for impairment. + References No definition available. + Details
Name: | cdw_GoodwillImpairmentTestIncomeApproachWeight
Namespace Prefix: | cdw_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The weight given the Market Approach in calculating the fair value of goodwill for a given reporting unit as part of the test for impairment. + References No definition available. + Details
Name: | cdw_GoodwillImpairmentTestMarketApproachWeight
Namespace Prefix: | cdw_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Long-Term Consolidated Annual Growth Rate + References No definition available. + Details
Name: | cdw_LongTermConsolidatedAnnualGrowthRate
Namespace Prefix: | cdw_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of operating segments which do not meet reportable unit quantitative threshold + References No definition available. + Details
Name: | cdw_NumberOfOperatingSegmentsWhichDoNotMeetReportableUnitQuantitativeThreshold
Namespace Prefix: | cdw_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The fair value of the reporting unit in excess of carrying value, expessed as a percent. + References No definition available. + Details
Name: | cdw_ReportingUnitFairValueInExcessOfCarryingValue
Namespace Prefix: | cdw_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Years Forecasted in Goodwill Impairment Income Approach + References No definition available. + Details
Name: | cdw_YearsForecastedInGoodwillImpairmentIncomeApproach
Namespace Prefix: | cdw_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References No definition available. + Details
Name: | us-gaap_NumberOfReportableSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | cdw_ReportingUnitsAxis=cdw_CorporateReportingUnitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | cdw_ReportingUnitsAxis=cdw_PublicReportingUnitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=cdw_CanadaOperatingSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=cdw_CDWAdvancedServicesOperatingSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |