v2.4.1.9

Supplemental Guarantor Information Consolidating Statements of Operations (Details) (USD $) | 3 Months Ended | 12 Months Ended
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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
Supplemental Guarantor Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term Debt, Gross | $ 3,192,400,000 us-gaap_DebtInstrumentCarryingAmount |  |  |  |  |  |  |  |  |  |  |  | $ 3,192,400,000 us-gaap_DebtInstrumentCarryingAmount |  |  |
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
Cost of sales |  |  |  |  |  |  |  |  |  |  |  |  | 10,153,200,000 us-gaap_CostOfGoodsAndServicesSold | 9,008,300,000 us-gaap_CostOfGoodsAndServicesSold |  | 8,458,600,000 us-gaap_CostOfGoodsAndServicesSold
Gross Profit | 491,900,000 us-gaap_GrossProfit | 507,300,000 us-gaap_GrossProfit | 496,900,000 us-gaap_GrossProfit | 425,200,000 us-gaap_GrossProfit | 448,300,000 us-gaap_GrossProfit |  | 458,400,000 us-gaap_GrossProfit |  | 451,600,000 us-gaap_GrossProfit |  | 402,000,000 us-gaap_GrossProfit |  | 1,921,300,000 us-gaap_GrossProfit | 1,760,300,000 us-gaap_GrossProfit |  | 1,669,600,000 us-gaap_GrossProfit
Selling and administrative expenses |  |  |  |  |  |  |  |  |  |  |  |  | 1,110,300,000 us-gaap_SellingGeneralAndAdministrativeExpense | 1,120,900,000 us-gaap_SellingGeneralAndAdministrativeExpense |  | 1,029,500,000 us-gaap_SellingGeneralAndAdministrativeExpense
Advertising expense |  |  |  |  |  |  |  |  |  |  |  |  | 138,000,000 us-gaap_AdvertisingExpense | 130,800,000 us-gaap_AdvertisingExpense |  | 129,500,000 us-gaap_AdvertisingExpense
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
Interest Income (Expense), Net |  |  |  |  |  |  |  |  |  |  |  |  | 197,300,000 us-gaap_InterestIncomeExpenseNet | 250,100,000 us-gaap_InterestIncomeExpenseNet |  | 307,400,000 us-gaap_InterestIncomeExpenseNet
Net (loss) gain on extinguishments of long-term debt |  |  |  |  |  |  |  |  |  |  |  |  | (90,700,000)us-gaap_GainsLossesOnExtinguishmentOfDebt | (64,000,000)us-gaap_GainsLossesOnExtinguishmentOfDebt |  | (17,200,000)us-gaap_GainsLossesOnExtinguishmentOfDebt
Other income, net |  |  |  |  |  |  |  |  |  |  |  |  | 2,700,000 us-gaap_OtherNonoperatingIncomeExpense | 1,000,000 us-gaap_OtherNonoperatingIncomeExpense |  | 100,000 us-gaap_OtherNonoperatingIncomeExpense
Income (loss) before income taxes |  |  |  |  |  |  |  |  |  |  |  |  | 387,700,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 195,500,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest |  | 186,100,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest
Income tax benefit (expense) |  |  |  |  |  |  |  |  |  |  |  |  | (142,800,000)us-gaap_IncomeTaxExpenseBenefit | (62,700,000)us-gaap_IncomeTaxExpenseBenefit |  | (67,100,000)us-gaap_IncomeTaxExpenseBenefit
Net income (loss) | 51,800,000 us-gaap_NetIncomeLoss | 55,600,000 us-gaap_NetIncomeLoss | 86,600,000 us-gaap_NetIncomeLoss | 50,900,000 us-gaap_NetIncomeLoss | 60,000,000 us-gaap_NetIncomeLoss | [1] | (2,200,000)us-gaap_NetIncomeLoss | [1] | 46,700,000 us-gaap_NetIncomeLoss | [1] | 28,300,000 us-gaap_NetIncomeLoss | [1] | 244,900,000 us-gaap_NetIncomeLoss | 132,800,000 us-gaap_NetIncomeLoss |  | 119,000,000 us-gaap_NetIncomeLoss
Parent Guarantor [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Supplemental Guarantor Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Cost of sales |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Gross Profit |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Selling and administrative expenses |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 24,400,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Advertising expense |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Income (loss) from operations |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (24,400,000)us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Interest Income (Expense), Net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net (loss) gain on extinguishments of long-term debt |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Management fee |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Other income, net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Income (loss) before income taxes |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (24,400,000)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Income tax benefit (expense) |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 9,200,000 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 244,900,000 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 148,000,000 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 119,000,000 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
(Loss) income before equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (15,200,000)cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 0 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  | 244,900,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 132,800,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | 119,000,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Subsidiary Issuer [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Supplemental Guarantor Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Cost of sales |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Gross Profit |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Selling and administrative expenses |  |  |  |  |  |  |  |  |  |  |  |  | 112,800,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 103,900,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | 103,700,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Advertising expense |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Income (loss) from operations |  |  |  |  |  |  |  |  |  |  |  |  | (112,800,000)us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (103,900,000)us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | (103,700,000)us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Interest Income (Expense), Net |  |  |  |  |  |  |  |  |  |  |  |  | (197,700,000)us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (250,600,000)us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | (308,000,000)us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Net (loss) gain on extinguishments of long-term debt |  |  |  |  |  |  |  |  |  |  |  |  | (90,700,000)us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (64,000,000)us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | (17,200,000)us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Management fee |  |  |  |  |  |  |  |  |  |  |  |  | 3,900,000 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 4,300,000 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | 3,800,000 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Other income, net |  |  |  |  |  |  |  |  |  |  |  |  | 1,200,000 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (500,000)us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | 0 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Income (loss) before income taxes |  |  |  |  |  |  |  |  |  |  |  |  | (396,100,000)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (414,700,000)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | (425,100,000)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Income tax benefit (expense) |  |  |  |  |  |  |  |  |  |  |  |  | 141,000,000 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 142,200,000 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | 210,600,000 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 500,000,000 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 420,500,000 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | 333,500,000 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
(Loss) income before equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | (255,100,000)cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (272,500,000)cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | (214,500,000)cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  | 244,900,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 148,000,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  | 119,000,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Guarantor Subsidiaries [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Supplemental Guarantor Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net |  |  |  |  |  |  |  |  |  |  |  |  | 11,542,300,000 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 10,293,300,000 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 9,683,000,000 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Cost of sales |  |  |  |  |  |  |  |  |  |  |  |  | 9,684,900,000 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 8,592,100,000 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 8,071,500,000 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Gross Profit |  |  |  |  |  |  |  |  |  |  |  |  | 1,857,400,000 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 1,701,200,000 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 1,611,500,000 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Selling and administrative expenses |  |  |  |  |  |  |  |  |  |  |  |  | 962,300,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 957,300,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 891,600,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Advertising expense |  |  |  |  |  |  |  |  |  |  |  |  | 134,000,000 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 126,800,000 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 125,100,000 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Income (loss) from operations |  |  |  |  |  |  |  |  |  |  |  |  | 761,100,000 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 617,100,000 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 594,800,000 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Interest Income (Expense), Net |  |  |  |  |  |  |  |  |  |  |  |  | 100,000 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 200,000 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 400,000 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net (loss) gain on extinguishments of long-term debt |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Management fee |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Other income, net |  |  |  |  |  |  |  |  |  |  |  |  | 1,500,000 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 1,200,000 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 200,000 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Income (loss) before income taxes |  |  |  |  |  |  |  |  |  |  |  |  | 762,700,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 618,500,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 595,400,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Income tax benefit (expense) |  |  |  |  |  |  |  |  |  |  |  |  | (278,100,000)us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (209,500,000)us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | (272,600,000)us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
(Loss) income before equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 484,600,000 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 409,000,000 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 322,800,000 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  | 484,600,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 409,000,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 322,800,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Non-Guarantor Subsidiaries [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Supplemental Guarantor Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net |  |  |  |  |  |  |  |  |  |  |  |  | 532,200,000 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 475,300,000 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 445,200,000 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Cost of sales |  |  |  |  |  |  |  |  |  |  |  |  | 468,300,000 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 416,200,000 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 387,100,000 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Gross Profit |  |  |  |  |  |  |  |  |  |  |  |  | 63,900,000 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 59,100,000 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 58,100,000 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Selling and administrative expenses |  |  |  |  |  |  |  |  |  |  |  |  | 35,200,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 35,300,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 34,200,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Advertising expense |  |  |  |  |  |  |  |  |  |  |  |  | 4,000,000 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 4,000,000 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 4,400,000 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Income (loss) from operations |  |  |  |  |  |  |  |  |  |  |  |  | 24,700,000 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 19,800,000 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 19,500,000 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Interest Income (Expense), Net |  |  |  |  |  |  |  |  |  |  |  |  | 300,000 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 300,000 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 200,000 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Net (loss) gain on extinguishments of long-term debt |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Management fee |  |  |  |  |  |  |  |  |  |  |  |  | (3,900,000)cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (4,300,000)cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | (3,800,000)cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Other income, net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 300,000 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | (100,000)us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Income (loss) before income taxes |  |  |  |  |  |  |  |  |  |  |  |  | 21,100,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 16,100,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 15,800,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Income tax benefit (expense) |  |  |  |  |  |  |  |  |  |  |  |  | (5,700,000)us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (4,600,000)us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | (5,100,000)us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
(Loss) income before equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 15,400,000 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 11,500,000 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 10,700,000 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  | 15,400,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 11,500,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 10,700,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Co-Issuer [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Supplemental Guarantor Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0.0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = cdw_CoIssuerMember
Cost of sales |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = cdw_CoIssuerMember
Gross Profit |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = cdw_CoIssuerMember
Selling and administrative expenses |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = cdw_CoIssuerMember
Advertising expense |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = cdw_CoIssuerMember
Income (loss) from operations |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = cdw_CoIssuerMember
Interest Income (Expense), Net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = cdw_CoIssuerMember
Net (loss) gain on extinguishments of long-term debt |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = cdw_CoIssuerMember
Management fee |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = cdw_CoIssuerMember
Other income, net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = cdw_CoIssuerMember
Income (loss) before income taxes |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = cdw_CoIssuerMember
Income tax benefit (expense) |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = cdw_CoIssuerMember
Equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = cdw_CoIssuerMember
(Loss) income before equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = cdw_CoIssuerMember
Net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = cdw_CoIssuerMember |  | 0 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = cdw_CoIssuerMember
Consolidating Adjustments [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Supplemental Guarantor Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Cost of sales |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Gross Profit |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Selling and administrative expenses |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Advertising expense |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Income (loss) from operations |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Interest Income (Expense), Net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Net (loss) gain on extinguishments of long-term debt |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Management fee |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Other income, net |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Income (loss) before income taxes |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Income tax benefit (expense) |  |  |  |  |  |  |  |  |  |  |  |  | 0 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | (744,900,000)cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | (568,500,000)cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | (452,500,000)cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
(Loss) income before equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | 0 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  | (744,900,000)us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | (568,500,000)us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  | (452,500,000)us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Consolidated [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Supplemental Guarantor Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, Net |  |  |  |  |  |  |  |  |  |  |  |  | 12,074,500,000 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 10,768,600,000 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | 10,128,200,000 us-gaap_SalesRevenueNet / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Cost of sales |  |  |  |  |  |  |  |  |  |  |  |  | 10,153,200,000 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 9,008,300,000 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | 8,458,600,000 us-gaap_CostOfGoodsAndServicesSold / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Gross Profit |  |  |  |  |  |  |  |  |  |  |  |  | 1,921,300,000 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 1,760,300,000 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | 1,669,600,000 us-gaap_GrossProfit / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Selling and administrative expenses |  |  |  |  |  |  |  |  |  |  |  |  | 1,110,300,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 1,120,900,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | 1,029,500,000 us-gaap_SellingGeneralAndAdministrativeExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Advertising expense |  |  |  |  |  |  |  |  |  |  |  |  | 138,000,000 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 130,800,000 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | 129,500,000 us-gaap_AdvertisingExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Income (loss) from operations |  |  |  |  |  |  |  |  |  |  |  |  | 673,000,000 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 508,600,000 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | 510,600,000 us-gaap_OperatingIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Interest Income (Expense), Net |  |  |  |  |  |  |  |  |  |  |  |  | (197,300,000)us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (250,100,000)us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | (307,400,000)us-gaap_InterestIncomeExpenseNet / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Net (loss) gain on extinguishments of long-term debt |  |  |  |  |  |  |  |  |  |  |  |  | (90,700,000)us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (64,000,000)us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | (17,200,000)us-gaap_GainsLossesOnExtinguishmentOfDebt / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Management fee |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | 0 cdw_ManagementFeeIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Other income, net |  |  |  |  |  |  |  |  |  |  |  |  | 2,700,000 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 1,000,000 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | 100,000 us-gaap_OtherNonoperatingIncomeExpense / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Income (loss) before income taxes |  |  |  |  |  |  |  |  |  |  |  |  | 387,700,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 195,500,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | 186,100,000 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Income tax benefit (expense) |  |  |  |  |  |  |  |  |  |  |  |  | (142,800,000)us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (62,700,000)us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | (67,100,000)us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | 0 cdw_EquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
(Loss) income before equity in earnings (loss) of subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  | 244,900,000 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 132,800,000 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | 119,000,000 cdw_IncomeLossBeforeEquityInEarningsLossOfSubsidiaries / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  | $ 244,900,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | $ 132,800,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | $ 119,000,000 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
[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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