v2.4.1.9

Deferred Compensation Plan (Details) (USD $) In Millions, except Share data, unless otherwise specified | 12 Months Ended | 3 Months Ended |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Mar. 31, 2016 | Aug. 01, 2013 | May 09, 2014 | Mar. 31, 2014 | Feb. 21, 2014 | Jan. 22, 2014 | Oct. 18, 2013 | Mar. 08, 2013 | Mar. 10, 2010
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
deferred compensation arrangement with individual, units authorized for issuance | 28,500 cdw_Deferredcompensationarrangementwithindividualunitsauthorizedforissuance |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred Compensation Arrangement with Individual, Units Outstanding | 28,500 cdw_DeferredCompensationArrangementwithIndividualUnitsOutstanding |  |  |  |  |  |  |  |  |  |  |  |  |
Redemption premium added to debt face amount, RDU plan | $ 0.1 cdw_RedemptionpremiumaddedtodebtfaceamountRDUplan |  | $ 1.4 cdw_RedemptionpremiumaddedtodebtfaceamountRDUplan |  |  |  |  |  |  |  |  |  |  |
RDU plan cash retention pool |  |  |  |  |  |  | 15.0 cdw_RDUplancashretentionpool |  |  |  |  |  |  |
Charge for payment of RDU Plan cash retention pool | 0 cdw_ChargeforpaymentofRDUPlancashretentionpool | [1] | 7.5 cdw_ChargeforpaymentofRDUPlancashretentionpool | [1] |  |  |  |  |  |  |  |  |  |
Deferred Compensation Arrangement with Individual, Requisite Service Period | 3 years 0 months 0 days |  |  |  |  |  |  |  |  |  |  |  |  |
RDU Plan, Compensation Expense | 8.8 us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense |  | 16.8 us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense |  | 8.4 us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense |  |  |  |  |  |  |  |  |
RDU Plan, Liability | 30.4 us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability |  | 21.8 us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability |  |  |  |  |  |  |  |  |  |  |
Subordinated Debt [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  |  |  |  |  |  | 324.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 42.5 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 50.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 20.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 30.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 155.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 50.0 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember | 28.5 us-gaap_DebtInstrumentRepurchasedFaceAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SubordinatedDebtMember
2015 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
RDU Plan, unrecognized compensation expense | 5 cdw_DeferredCompensationArrangementWithIndividualUnrecognizedCompensationExpense / cdw_PeriodofRecognitionAxis = cdw_A2015MemberDomain |  |  |  |  |  |  |  |  |  |  |  |  |
2016 through 2017 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
RDU Plan, unrecognized compensation expense | 3 cdw_DeferredCompensationArrangementWithIndividualUnrecognizedCompensationExpense / cdw_PeriodofRecognitionAxis = cdw_A2016through2017MemberMember |  |  |  |  |  |  |  |  |  |  |  |  |
Scenario, Forecast [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Second RDU Cash Retention Payment |  |  |  |  |  | $ 7.5 cdw_SecondRDUCashRetentionPayment / us-gaap_StatementScenarioAxis = us-gaap_ScenarioForecastMember |  |  |  |  |  |  |  |
[1] | See Note 12 for additional discussion of this transaction.

X
- Definition Charge for payment of RDU Plan cash retention pool + References No definition available. + Details
Name: | cdw_ChargeforpaymentofRDUPlancashretentionpool
Namespace Prefix: | cdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition deferred compensation arrangement with individual, units authorized for issuance + References No definition available. + Details
Name: | cdw_Deferredcompensationarrangementwithindividualunitsauthorizedforissuance
Namespace Prefix: | cdw_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Deferred Compensation Arrangement with Individual, Units Outstanding + References No definition available. + Details
Name: | cdw_DeferredCompensationArrangementwithIndividualUnitsOutstanding
Namespace Prefix: | cdw_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Deferred Compensation Arrangement with Individual, unrecognized compensation expense + References No definition available. + Details
Name: | cdw_DeferredCompensationArrangementWithIndividualUnrecognizedCompensationExpense
Namespace Prefix: | cdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition RDU plan cash retention pool + References No definition available. + Details
Name: | cdw_RDUplancashretentionpool
Namespace Prefix: | cdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Redemption premium added to debt face amount, RDU plan + References No definition available. + Details
Name: | cdw_RedemptionpremiumaddedtodebtfaceamountRDUplan
Namespace Prefix: | cdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Second RDU Cash Retention Payment + References No definition available. + Details
Name: | cdw_SecondRDUCashRetentionPayment
Namespace Prefix: | cdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Face (par) amount of the original debt instrument that was repurchased. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The compensation expense recognized during the period pertaining to the deferred compensation arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 710 -SubTopic 10 -Section 30 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363 + Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Definition The carrying amount of the liability as of the balance sheet date to an individual under a deferred compensation arrangement. This amount may be the result of periodic accruals made over the period of active employment, or reflect termination benefits resulting contractual terms or a death benefit. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 710 -SubTopic 10 -Section 30 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363 + Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Minimum period the individual is required to perform services to be fully vested under the deferred compensation arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 710 -SubTopic 10 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6409961&loc=d3e20487-108367 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_DeferredCompensationArrangementWithIndividualRequisiteServicePeriod1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | cdw_PeriodofRecognitionAxis=cdw_A2015MemberDomain
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | cdw_PeriodofRecognitionAxis=cdw_A2016through2017MemberMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_SubordinatedDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |