v2.4.1.9

Supplemental Guarantor Information Condensed Consolidating Statements of Cash Flows (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Supplemental Guarantor Information [Line Items] |  |  |
Net cash provided by (used in) operating activities | $ 435.0 us-gaap_NetCashProvidedByUsedInOperatingActivities | $ 366.3 us-gaap_NetCashProvidedByUsedInOperatingActivities | $ 317.4 us-gaap_NetCashProvidedByUsedInOperatingActivities
Capital expenditures | (55.0)us-gaap_PaymentsToAcquireProductiveAssets | (47.1)us-gaap_PaymentsToAcquireProductiveAssets | (41.4)us-gaap_PaymentsToAcquireProductiveAssets
Payments to Acquire Equity Method Investments | (86.8)us-gaap_PaymentsToAcquireEquityMethodInvestments | 0 us-gaap_PaymentsToAcquireEquityMethodInvestments | 0 us-gaap_PaymentsToAcquireEquityMethodInvestments
Premium payments on interest rate cap agreements | (2.1)us-gaap_PaymentsForDerivativeInstrumentInvestingActivities | 0 us-gaap_PaymentsForDerivativeInstrumentInvestingActivities | (0.3)us-gaap_PaymentsForDerivativeInstrumentInvestingActivities
Net cash used in investing activities | (164.8)us-gaap_NetCashProvidedByUsedInInvestingActivities | (47.1)us-gaap_NetCashProvidedByUsedInInvestingActivities | (41.7)us-gaap_NetCashProvidedByUsedInInvestingActivities
Proceeds from borrowings under revolving credit facility | 0 us-gaap_ProceedsFromLinesOfCredit | 63.0 us-gaap_ProceedsFromLinesOfCredit | 289.0 us-gaap_ProceedsFromLinesOfCredit
Repayments of borrowings under revolving credit facility | 0 us-gaap_RepaymentsOfLinesOfCredit | (63.0)us-gaap_RepaymentsOfLinesOfCredit | (289.0)us-gaap_RepaymentsOfLinesOfCredit
Repayments of long-term debt | (15.4)us-gaap_RepaymentsOfSecuredDebt | (51.1)us-gaap_RepaymentsOfSecuredDebt | (201.0)us-gaap_RepaymentsOfSecuredDebt
Proceeds from issuance of long-term debt | 1,175.0 us-gaap_ProceedsFromIssuanceOfLongTermDebt | 1,535.2 us-gaap_ProceedsFromIssuanceOfLongTermDebt | 135.7 us-gaap_ProceedsFromIssuanceOfLongTermDebt
Payments to extinguish long-term debt | (1,299.0)us-gaap_RepaymentsOfLongTermDebt | (2,047.4)us-gaap_RepaymentsOfLongTermDebt | (243.2)us-gaap_RepaymentsOfLongTermDebt
Payments of debt financing costs | (21.9)us-gaap_PaymentsOfFinancingCosts | (6.1)us-gaap_PaymentsOfFinancingCosts | (2.1)us-gaap_PaymentsOfFinancingCosts
Net change in accounts payable-inventory financing | 75.5 cdw_NetChangeInAccountsPayableInventoryFinancing | 7.4 cdw_NetChangeInAccountsPayableInventoryFinancing | (29.5)cdw_NetChangeInAccountsPayableInventoryFinancing
Payment of incentive compensation plan withholding taxes | 0 us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation | (24.1)us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation | 0 us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation
Proceeds from Stock Options Exercised | 1.3 us-gaap_ProceedsFromStockOptionsExercised | 0 us-gaap_ProceedsFromStockOptionsExercised | 0 us-gaap_ProceedsFromStockOptionsExercised
Net proceeds from issuance of common shares | 0 us-gaap_ProceedsFromIssuanceOfCommonStock | 424.7 us-gaap_ProceedsFromIssuanceOfCommonStock | 0 us-gaap_ProceedsFromIssuanceOfCommonStock
Proceeds from Coworker Stock Purchase Plan | 5.8 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans | 0 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans | 0 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans
Dividends paid | (33.6)us-gaap_PaymentsOfDividendsCommonStock | (7.3)us-gaap_PaymentsOfDividendsCommonStock | 0 us-gaap_PaymentsOfDividendsCommonStock
Excess Tax Benefit from Share-based Compensation, Financing Activities | 0.3 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities | 0.6 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities | 0 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities
Net cash provided by (used in) financing activities | (112.0)us-gaap_NetCashProvidedByUsedInFinancingActivities | (168.3)us-gaap_NetCashProvidedByUsedInFinancingActivities | (338.0)us-gaap_NetCashProvidedByUsedInFinancingActivities
Effect of exchange rate changes on cash and cash equivalents | (1.8)us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents | (0.7)us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents | 0.3 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents
Net increase (decrease) in cash and cash equivalents | 156.4 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease | 150.2 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease | (62.0)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease
Cash and cash equivalents - beginning of period | 188.1 us-gaap_CashAndCashEquivalentsAtCarryingValue | 37.9 us-gaap_CashAndCashEquivalentsAtCarryingValue | 99.9 us-gaap_CashAndCashEquivalentsAtCarryingValue
Cash and cash equivalents - end of period | 344.5 us-gaap_CashAndCashEquivalentsAtCarryingValue | 188.1 us-gaap_CashAndCashEquivalentsAtCarryingValue | 37.9 us-gaap_CashAndCashEquivalentsAtCarryingValue
Payment of accrued charitable contribution related to the MPK Coworker Incentive Plan II | (20.9)cdw_PaymentofaccruedcharitablecontributionrelatedtotheMPKCoworkerIncentivePlanII | 0 cdw_PaymentofaccruedcharitablecontributionrelatedtotheMPKCoworkerIncentivePlanII | 0 cdw_PaymentofaccruedcharitablecontributionrelatedtotheMPKCoworkerIncentivePlanII
Parent Guarantor [Member] |  |  |
Supplemental Guarantor Information [Line Items] |  |  |
Net cash provided by (used in) operating activities | 0 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (15.2)us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Capital expenditures | 0 us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Payments to Acquire Equity Method Investments | 0 us-gaap_PaymentsToAcquireEquityMethodInvestments / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Premium payments on interest rate cap agreements |  |  | 0 us-gaap_PaymentsForDerivativeInstrumentInvestingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net cash used in investing activities | 0 us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Proceeds from borrowings under revolving credit facility |  | 0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Repayments of borrowings under revolving credit facility |  | 0 us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Repayments of long-term debt | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Proceeds from issuance of long-term debt | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Payments to extinguish long-term debt | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Payments of debt financing costs | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net change in accounts payable-inventory financing | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Payment of incentive compensation plan withholding taxes |  | 0 us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Proceeds from Stock Options Exercised | 0 us-gaap_ProceedsFromStockOptionsExercised / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Net proceeds from issuance of common shares |  | 424.7 us-gaap_ProceedsFromIssuanceOfCommonStock / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Proceeds from Coworker Stock Purchase Plan | 0 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Dividends paid | (33.6)us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (7.3)us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Excess Tax Benefit from Share-based Compensation, Financing Activities | 0 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Advances to (from) affiliates | 33.6 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (402.2)cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Other financing activities |  | 0 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net cash provided by (used in) financing activities | 0 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 15.2 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Effect of exchange rate changes on cash and cash equivalents | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net increase (decrease) in cash and cash equivalents | 0 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Cash and cash equivalents - beginning of period | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Cash and cash equivalents - end of period | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Payment of accrued charitable contribution related to the MPK Coworker Incentive Plan II | 0 cdw_PaymentofaccruedcharitablecontributionrelatedtotheMPKCoworkerIncentivePlanII / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Payments for Derivative Instrument, Financing Activities | 0 us-gaap_PaymentsForDerivativeInstrumentFinancingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Subsidiary Issuer [Member] |  |  |
Supplemental Guarantor Information [Line Items] |  |  |
Net cash provided by (used in) operating activities | (120.4)us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (130.3)us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (204.3)us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Capital expenditures | (47.9)us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (40.8)us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (27.0)us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Payments to Acquire Equity Method Investments | (86.8)us-gaap_PaymentsToAcquireEquityMethodInvestments / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  |
Premium payments on interest rate cap agreements |  |  | (0.3)us-gaap_PaymentsForDerivativeInstrumentInvestingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Net cash used in investing activities | (157.7)us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (40.8)us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (27.3)us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Proceeds from borrowings under revolving credit facility |  | 63.0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 289.0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Repayments of borrowings under revolving credit facility |  | (63.0)us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (289.0)us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Repayments of long-term debt | (15.4)us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (51.1)us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (201.0)us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Proceeds from issuance of long-term debt | 1,175.0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 1,535.2 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 135.7 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Payments to extinguish long-term debt | (1,299.0)us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (2,047.4)us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (243.2)us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Payments of debt financing costs | (21.9)us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (6.1)us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (2.1)us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Net change in accounts payable-inventory financing | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Payment of incentive compensation plan withholding taxes |  | (4.0)us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |
Proceeds from Stock Options Exercised | 1.3 us-gaap_ProceedsFromStockOptionsExercised / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  |
Net proceeds from issuance of common shares |  | 0 us-gaap_ProceedsFromIssuanceOfCommonStock / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |
Proceeds from Coworker Stock Purchase Plan | 5.8 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  |
Dividends paid | 0 us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 0 us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |
Excess Tax Benefit from Share-based Compensation, Financing Activities | 0.3 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  |
Advances to (from) affiliates | 581.9 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 892.6 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 486.0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Other financing activities |  | 0.4 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 2.1 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Net cash provided by (used in) financing activities | 428.0 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 319.6 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 177.5 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Effect of exchange rate changes on cash and cash equivalents | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Net increase (decrease) in cash and cash equivalents | 149.9 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 148.5 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | (54.1)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Cash and cash equivalents - beginning of period | 196.5 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 48.0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 102.1 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Cash and cash equivalents - end of period | 346.4 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 196.5 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember | 48.0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember
Payment of accrued charitable contribution related to the MPK Coworker Incentive Plan II | (20.9)cdw_PaymentofaccruedcharitablecontributionrelatedtotheMPKCoworkerIncentivePlanII / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  |
Payments for Derivative Instrument, Financing Activities | 2.1 us-gaap_PaymentsForDerivativeInstrumentFinancingActivities / dei_LegalEntityAxis = us-gaap_SubsidiaryIssuerMember |  |
Guarantor Subsidiaries [Member] |  |  |
Supplemental Guarantor Information [Line Items] |  |  |
Net cash provided by (used in) operating activities | 547.7 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 508.8 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 514.2 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Capital expenditures | (7.1)us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (6.2)us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (14.0)us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Payments to Acquire Equity Method Investments | 0 us-gaap_PaymentsToAcquireEquityMethodInvestments / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  |
Premium payments on interest rate cap agreements |  |  | 0 us-gaap_PaymentsForDerivativeInstrumentInvestingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net cash used in investing activities | (7.1)us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (6.2)us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (14.0)us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Proceeds from borrowings under revolving credit facility |  | 0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Repayments of borrowings under revolving credit facility |  | 0 us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Repayments of long-term debt | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Proceeds from issuance of long-term debt | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Payments to extinguish long-term debt | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Payments of debt financing costs | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net change in accounts payable-inventory financing | 75.5 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 7.4 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (29.5)cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Payment of incentive compensation plan withholding taxes |  | (19.6)us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |
Proceeds from Stock Options Exercised | 0 us-gaap_ProceedsFromStockOptionsExercised / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  |
Net proceeds from issuance of common shares |  | 0 us-gaap_ProceedsFromIssuanceOfCommonStock / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |
Proceeds from Coworker Stock Purchase Plan | 0 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  |
Dividends paid | 0 us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |
Excess Tax Benefit from Share-based Compensation, Financing Activities | 0 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  |
Advances to (from) affiliates | (616.1)cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (490.4)cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (486.5)cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Other financing activities |  | 0 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net cash provided by (used in) financing activities | (540.6)us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (502.6)us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (516.0)us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Effect of exchange rate changes on cash and cash equivalents | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net increase (decrease) in cash and cash equivalents | 0 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (15.8)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Cash and cash equivalents - beginning of period | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 15.8 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Cash and cash equivalents - end of period | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Payment of accrued charitable contribution related to the MPK Coworker Incentive Plan II | 0 cdw_PaymentofaccruedcharitablecontributionrelatedtotheMPKCoworkerIncentivePlanII / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  |
Payments for Derivative Instrument, Financing Activities | 0 us-gaap_PaymentsForDerivativeInstrumentFinancingActivities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  |
Non-Guarantor Subsidiaries [Member] |  |  |
Supplemental Guarantor Information [Line Items] |  |  |
Net cash provided by (used in) operating activities | 11.8 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 5.5 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 1.3 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Capital expenditures | 0 us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (0.1)us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (0.4)us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Payments to Acquire Equity Method Investments | 0 us-gaap_PaymentsToAcquireEquityMethodInvestments / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  |
Premium payments on interest rate cap agreements |  |  | 0 us-gaap_PaymentsForDerivativeInstrumentInvestingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Net cash used in investing activities | 0 us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (0.1)us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (0.4)us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Proceeds from borrowings under revolving credit facility |  | 0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Repayments of borrowings under revolving credit facility |  | 0 us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Repayments of long-term debt | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Proceeds from issuance of long-term debt | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Payments to extinguish long-term debt | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Payments of debt financing costs | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Net change in accounts payable-inventory financing | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Payment of incentive compensation plan withholding taxes |  | (0.5)us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |
Proceeds from Stock Options Exercised | 0 us-gaap_ProceedsFromStockOptionsExercised / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  |
Net proceeds from issuance of common shares |  | 0 us-gaap_ProceedsFromIssuanceOfCommonStock / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |
Proceeds from Coworker Stock Purchase Plan | 0 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  |
Dividends paid | 0 us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |
Excess Tax Benefit from Share-based Compensation, Financing Activities | 0 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  |
Advances to (from) affiliates | 0.6 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0.5 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Other financing activities |  | 0 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Net cash provided by (used in) financing activities | 0.6 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (0.5)us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0.5 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Effect of exchange rate changes on cash and cash equivalents | (1.8)us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (0.7)us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 0.3 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Net increase (decrease) in cash and cash equivalents | 10.6 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 4.2 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 1.7 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Cash and cash equivalents - beginning of period | 14.0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 9.8 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 8.1 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Cash and cash equivalents - end of period | 24.6 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 14.0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 9.8 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Payment of accrued charitable contribution related to the MPK Coworker Incentive Plan II | 0 cdw_PaymentofaccruedcharitablecontributionrelatedtotheMPKCoworkerIncentivePlanII / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  |
Payments for Derivative Instrument, Financing Activities | 0 us-gaap_PaymentsForDerivativeInstrumentFinancingActivities / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  |
Co-Issuer [Member] |  |  |
Supplemental Guarantor Information [Line Items] |  |  |
Net cash provided by (used in) operating activities | 0 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember
Capital expenditures | 0 us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = cdw_CoIssuerMember
Payments to Acquire Equity Method Investments | 0 us-gaap_PaymentsToAcquireEquityMethodInvestments / dei_LegalEntityAxis = cdw_CoIssuerMember |  |
Premium payments on interest rate cap agreements |  |  | 0 us-gaap_PaymentsForDerivativeInstrumentInvestingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember
Net cash used in investing activities | 0 us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember
Proceeds from borrowings under revolving credit facility |  | 0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = cdw_CoIssuerMember
Repayments of borrowings under revolving credit facility |  | 0 us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = cdw_CoIssuerMember
Repayments of long-term debt | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = cdw_CoIssuerMember
Proceeds from issuance of long-term debt | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = cdw_CoIssuerMember
Payments to extinguish long-term debt | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = cdw_CoIssuerMember
Payments of debt financing costs | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = cdw_CoIssuerMember
Net change in accounts payable-inventory financing | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = cdw_CoIssuerMember
Payment of incentive compensation plan withholding taxes |  | 0 us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation / dei_LegalEntityAxis = cdw_CoIssuerMember |
Proceeds from Stock Options Exercised | 0 us-gaap_ProceedsFromStockOptionsExercised / dei_LegalEntityAxis = cdw_CoIssuerMember |  |
Net proceeds from issuance of common shares |  | 0 us-gaap_ProceedsFromIssuanceOfCommonStock / dei_LegalEntityAxis = cdw_CoIssuerMember |
Proceeds from Coworker Stock Purchase Plan | 0 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans / dei_LegalEntityAxis = cdw_CoIssuerMember |  |
Dividends paid | 0 us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = cdw_CoIssuerMember |
Excess Tax Benefit from Share-based Compensation, Financing Activities | 0 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember |  |
Advances to (from) affiliates | 0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = cdw_CoIssuerMember
Other financing activities |  | 0 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember
Net cash provided by (used in) financing activities | 0 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember
Effect of exchange rate changes on cash and cash equivalents | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = cdw_CoIssuerMember
Net increase (decrease) in cash and cash equivalents | 0 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = cdw_CoIssuerMember
Cash and cash equivalents - beginning of period | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = cdw_CoIssuerMember
Cash and cash equivalents - end of period | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = cdw_CoIssuerMember | 0 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = cdw_CoIssuerMember
Payment of accrued charitable contribution related to the MPK Coworker Incentive Plan II | 0 cdw_PaymentofaccruedcharitablecontributionrelatedtotheMPKCoworkerIncentivePlanII / dei_LegalEntityAxis = cdw_CoIssuerMember |  |
Payments for Derivative Instrument, Financing Activities | 0 us-gaap_PaymentsForDerivativeInstrumentFinancingActivities / dei_LegalEntityAxis = cdw_CoIssuerMember |  |
Consolidating Adjustments [Member] |  |  |
Supplemental Guarantor Information [Line Items] |  |  |
Net cash provided by (used in) operating activities | (4.1)us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | (2.5)us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 6.2 us-gaap_NetCashProvidedByUsedInOperatingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Capital expenditures | 0 us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Payments to Acquire Equity Method Investments | 0 us-gaap_PaymentsToAcquireEquityMethodInvestments / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  |
Premium payments on interest rate cap agreements |  |  | 0 us-gaap_PaymentsForDerivativeInstrumentInvestingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Net cash used in investing activities | 0 us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_NetCashProvidedByUsedInInvestingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Proceeds from borrowings under revolving credit facility |  | 0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Repayments of borrowings under revolving credit facility |  | 0 us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Repayments of long-term debt | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_RepaymentsOfSecuredDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Proceeds from issuance of long-term debt | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Payments to extinguish long-term debt | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Payments of debt financing costs | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Net change in accounts payable-inventory financing | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Payment of incentive compensation plan withholding taxes |  | 0 us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |
Proceeds from Stock Options Exercised | 0 us-gaap_ProceedsFromStockOptionsExercised / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  |
Net proceeds from issuance of common shares |  | 0 us-gaap_ProceedsFromIssuanceOfCommonStock / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |
Proceeds from Coworker Stock Purchase Plan | 0 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  |
Dividends paid | 0 us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |
Advances to (from) affiliates | 0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Other financing activities |  | 0 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Net cash provided by (used in) financing activities | 0 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_NetCashProvidedByUsedInFinancingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Effect of exchange rate changes on cash and cash equivalents | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 0 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Net increase (decrease) in cash and cash equivalents | (4.1)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | (2.5)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | 6.2 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Cash and cash equivalents - beginning of period | (22.4)us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | (19.9)us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | (26.1)us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Cash and cash equivalents - end of period | (26.5)us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | (22.4)us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember | (19.9)us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember
Payment of accrued charitable contribution related to the MPK Coworker Incentive Plan II | 0 cdw_PaymentofaccruedcharitablecontributionrelatedtotheMPKCoworkerIncentivePlanII / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  |
Payments for Derivative Instrument, Financing Activities | 0 us-gaap_PaymentsForDerivativeInstrumentFinancingActivities / dei_LegalEntityAxis = us-gaap_ConsolidationEliminationsMember |  |
Consolidated [Member] |  |  |
Supplemental Guarantor Information [Line Items] |  |  |
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Capital expenditures | (55.0)us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (47.1)us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (41.4)us-gaap_PaymentsToAcquireProductiveAssets / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Payments to Acquire Equity Method Investments | (86.8)us-gaap_PaymentsToAcquireEquityMethodInvestments / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  |
Premium payments on interest rate cap agreements | (2.1)us-gaap_PaymentsForDerivativeInstrumentInvestingActivities / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  | (0.3)us-gaap_PaymentsForDerivativeInstrumentInvestingActivities / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
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Proceeds from borrowings under revolving credit facility |  | 63.0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 289.0 us-gaap_ProceedsFromLinesOfCredit / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Repayments of borrowings under revolving credit facility |  | (63.0)us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (289.0)us-gaap_RepaymentsOfLinesOfCredit / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
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Proceeds from issuance of long-term debt | 1,175.0 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 1,535.2 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 135.7 us-gaap_ProceedsFromIssuanceOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Payments to extinguish long-term debt | (1,299.0)us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (2,047.4)us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (243.2)us-gaap_RepaymentsOfLongTermDebt / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Payments of debt financing costs | (21.9)us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (6.1)us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (2.1)us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Net change in accounts payable-inventory financing | 75.5 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 7.4 cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (29.5)cdw_NetChangeInAccountsPayableInventoryFinancing / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Payment of incentive compensation plan withholding taxes |  | (24.1)us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |
Proceeds from Stock Options Exercised | 1.3 us-gaap_ProceedsFromStockOptionsExercised / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  |
Net proceeds from issuance of common shares | 5.8 us-gaap_ProceedsFromIssuanceOfCommonStock / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 424.7 us-gaap_ProceedsFromIssuanceOfCommonStock / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |
Dividends paid | (33.6)us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (7.3)us-gaap_PaymentsOfDividendsCommonStock / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |
Excess Tax Benefit from Share-based Compensation, Financing Activities | 0.3 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  |
Advances to (from) affiliates | 0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 0 cdw_AdvancesToFromAffiliates / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
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Effect of exchange rate changes on cash and cash equivalents | (1.8)us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (0.7)us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 0.3 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Net increase (decrease) in cash and cash equivalents | 156.4 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 150.2 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | (62.0)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Cash and cash equivalents - beginning of period | 188.1 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 37.9 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 99.9 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Cash and cash equivalents - end of period | 344.5 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 188.1 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember | 37.9 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember
Payment of accrued charitable contribution related to the MPK Coworker Incentive Plan II | $ (20.9)cdw_PaymentofaccruedcharitablecontributionrelatedtotheMPKCoworkerIncentivePlanII / dei_LegalEntityAxis = us-gaap_ConsolidatedEntitiesMember |  |

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- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 + Details
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- Definition Amount of increase (decrease) from the effect of exchange rate changes on cash and cash equivalent balances held in foreign currencies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 230 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450594&loc=d3e33268-110906 + Details
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- Definition Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(f)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph f -Article 4 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 + Details
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- Definition The net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 + Details
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- Definition The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 + Details
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