v2.4.1.9

Segment Information Segment Reporting (Details) (USD $) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
IPO and Secondary-offering related expenses |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 75,000,000 cdw_IPOandSecondaryofferingrelatedexpenses |  |
Revenue, Net | 3,050,100,000 us-gaap_SalesRevenueNet | 3,266,100,000 us-gaap_SalesRevenueNet | 3,106,000,000 us-gaap_SalesRevenueNet | 2,652,300,000 us-gaap_SalesRevenueNet | 2,713,300,000 us-gaap_SalesRevenueNet |  | 2,864,300,000 us-gaap_SalesRevenueNet |  | 2,779,300,000 us-gaap_SalesRevenueNet |  | 2,411,700,000 us-gaap_SalesRevenueNet |  | 12,074,500,000 us-gaap_SalesRevenueNet | 10,768,600,000 us-gaap_SalesRevenueNet |  | 10,128,200,000 us-gaap_SalesRevenueNet
Income (loss) from operations | 164,300,000 us-gaap_OperatingIncomeLoss | 184,700,000 us-gaap_OperatingIncomeLoss | 188,200,000 us-gaap_OperatingIncomeLoss | 135,800,000 us-gaap_OperatingIncomeLoss | 142,000,000 us-gaap_OperatingIncomeLoss | [1] | 92,900,000 us-gaap_OperatingIncomeLoss | [1] | 153,600,000 us-gaap_OperatingIncomeLoss | [1] | 120,100,000 us-gaap_OperatingIncomeLoss | [1] | 673,000,000 us-gaap_OperatingIncomeLoss | 508,600,000 us-gaap_OperatingIncomeLoss | [2] | 510,600,000 us-gaap_OperatingIncomeLoss
Depreciation and amortization expense |  |  |  |  |  |  |  |  |  |  |  |  | (207,900,000)us-gaap_DepreciationDepletionAndAmortization | (208,200,000)us-gaap_DepreciationDepletionAndAmortization |  | (210,200,000)us-gaap_DepreciationDepletionAndAmortization
Segment Reporting Information, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Reportable Segments |  |  |  |  |  |  |  |  |  |  |  |  | 2 us-gaap_NumberOfReportableSegments |  |  |
Number of operating segments which do not meet reporting unit quantitative threshold |  |  |  |  |  |  |  |  |  |  |  |  | 3 cdw_NumberOfOperatingSegmentsWhichDoNotMeetReportableUnitQuantitativeThreshold |  |  |
Net sales to the federal government, Percentage |  |  |  |  |  |  |  |  |  |  |  |  | 7.00%us-gaap_ConcentrationRiskPercentage1 | 7.00%us-gaap_ConcentrationRiskPercentage1 |  | 10.00%us-gaap_ConcentrationRiskPercentage1
Net sales to customers outside of the US, Percent |  |  |  |  |  |  |  |  |  |  |  |  | 4.00%cdw_NetSalesToCustomersOutsideOfUsPercent | 4.00%cdw_NetSalesToCustomersOutsideOfUsPercent |  | 4.00%cdw_NetSalesToCustomersOutsideOfUsPercent
Long-Lived Assets in Foreign Countries, Percent | 1.00%cdw_LongLivedAssetsInForeignCountriesPercent |  |  |  | 1.00%cdw_LongLivedAssetsInForeignCountriesPercent |  |  |  |  |  |  |  | 1.00%cdw_LongLivedAssetsInForeignCountriesPercent | 1.00%cdw_LongLivedAssetsInForeignCountriesPercent |  |
Equity Method Investment, Ownership Percentage | 35.00%us-gaap_EquityMethodInvestmentOwnershipPercentage |  |  |  |  |  |  |  |  |  |  |  | 35.00%us-gaap_EquityMethodInvestmentOwnershipPercentage |  |  |
Public Segment: Government Agencies, Education and Healthcare [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net |  |  |  |  |  |  |  |  |  |  |  |  | 4,879,400,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicSegmentGovernmentAgenciesEducationandHealthcareMember | 4,164,500,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicSegmentGovernmentAgenciesEducationandHealthcareMember |  | 4,023,000,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicSegmentGovernmentAgenciesEducationandHealthcareMember
Income (loss) from operations |  |  |  |  |  |  |  |  |  |  |  |  | 313,200,000 us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicSegmentGovernmentAgenciesEducationandHealthcareMember | 246,500,000 us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicSegmentGovernmentAgenciesEducationandHealthcareMember | [2] | 246,700,000 us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicSegmentGovernmentAgenciesEducationandHealthcareMember
Depreciation and amortization expense |  |  |  |  |  |  |  |  |  |  |  |  | (43,800,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicSegmentGovernmentAgenciesEducationandHealthcareMember | (44,000,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicSegmentGovernmentAgenciesEducationandHealthcareMember |  | (44,000,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicSegmentGovernmentAgenciesEducationandHealthcareMember
Corporate [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net | 1,691,000,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentMember | 1,622,700,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentMember | 1,656,200,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentMember | 1,505,600,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentMember | 1,553,000,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentMember |  | 1,465,800,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentMember |  | 1,537,400,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentMember |  | 1,403,900,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentMember |  |  |  |  |
Segment Reporting Information, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
IPO- and secondary-offering related expenses |  |  |  |  |  |  |  |  |  |  |  |  |  | 26,400,000 cdw_IPOandsecondaryofferingrelatedexpenses / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentMember |  |
Public [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net | 1,169,100,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember | 1,468,800,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember | 1,271,600,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember | 969,900,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember | 990,500,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember |  | 1,244,600,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember |  | 1,082,600,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember |  | 846,800,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember |  |  |  |  |
Segment Reporting Information, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
IPO- and secondary-offering related expenses |  |  |  |  |  |  |  |  |  |  |  |  |  | 14,400,000 cdw_IPOandsecondaryofferingrelatedexpenses / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember |  |
Other [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net | 190,000,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 174,600,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 178,200,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 176,800,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 169,800,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember |  | 153,900,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember |  | 159,300,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember |  | 161,000,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember |  | 719,600,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 644,000,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember |  | 592,400,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Income (loss) from operations |  |  |  |  |  |  |  |  |  |  |  |  | 32,900,000 us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 27,200,000 us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | [2] | 18,600,000 us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Depreciation and amortization expense |  |  |  |  |  |  |  |  |  |  |  |  | (8,800,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | (8,600,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember |  | (9,300,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Segment Reporting Information, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
IPO- and secondary-offering related expenses |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,600,000 cdw_IPOandsecondaryofferingrelatedexpenses / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember |  |
Corporate, Non-Segment [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateNonSegmentMember | 0 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateNonSegmentMember |  | 0 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateNonSegmentMember
Income (loss) from operations |  |  |  |  |  |  |  |  |  |  |  |  | (112,900,000)us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateNonSegmentMember | (128,400,000)us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateNonSegmentMember | [2] | (103,700,000)us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateNonSegmentMember
Depreciation and amortization expense |  |  |  |  |  |  |  |  |  |  |  |  | (59,000,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateNonSegmentMember | (58,300,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateNonSegmentMember |  | (59,300,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateNonSegmentMember
Segment Reporting Information, Additional Information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
IPO- and secondary-offering related expenses |  |  |  |  |  |  |  |  |  |  |  |  |  | 30,600,000 cdw_IPOandsecondaryofferingrelatedexpenses / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateNonSegmentMember |  |
Corporate Segment: Private Sector Business [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net |  |  |  |  |  |  |  |  |  |  |  |  | 6,475,500,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentPrivateSectorBusinessMember | 5,960,100,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentPrivateSectorBusinessMember |  | 5,512,800,000 us-gaap_SalesRevenueNet / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentPrivateSectorBusinessMember
Income (loss) from operations |  |  |  |  |  |  |  |  |  |  |  |  | 439,800,000 us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentPrivateSectorBusinessMember | 363,300,000 us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentPrivateSectorBusinessMember | [2] | 349,000,000 us-gaap_OperatingIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentPrivateSectorBusinessMember
Depreciation and amortization expense |  |  |  |  |  |  |  |  |  |  |  |  | (96,300,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentPrivateSectorBusinessMember | (97,300,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentPrivateSectorBusinessMember |  | (97,600,000)us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = cdw_CorporateSegmentPrivateSectorBusinessMember
Federal [Member] | Public [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net |  |  |  |  |  |  |  |  |  |  |  |  | $ 884,200,000 us-gaap_SalesRevenueNet / cdw_PublicAxis = cdw_FederalMember / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember | $ 764,400,000 us-gaap_SalesRevenueNet / cdw_PublicAxis = cdw_FederalMember / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember |  | $ 964,700,000 us-gaap_SalesRevenueNet / cdw_PublicAxis = cdw_FederalMember / us-gaap_StatementBusinessSegmentsAxis = cdw_PublicMember
[1] | (3)The third quarter of 2013 included pre-tax IPO-related charges of $74.1 million. See Note 9 for additional discussion of the IPO.
[2] | (1) Includes $75.0 million of IPO- and secondary-offering related expenses, as follows: Corporate $26.4 million; Public $14.4 million; Other $3.6 million; and Headquarters $30.6 million.

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