v2.4.0.8

Shareholders Equity IPO and Secondary-Offering-Related Expenses Table (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2014 | Sep. 30, 2013 | Sep. 30, 2014 | Sep. 30, 2013 | Dec. 31, 2013
IPO and Secondary-Offering- Related Expenses [Line Items] |  |  |  |  |  |  |  |  |
Accelerated share based compensation expense and related employer payroll taxes | $ 0 |  | $ 40.7 |  | $ 0 |  | $ 40.7 |  |
Charge for payment of RDU Plan cash retention pool | 0 |  | 7.5 |  | 0 |  | 7.5 |  | 7.5
Net proceeds used for termination of management services agreement | 0 |  | 24.4 |  | 0 |  | 24.4 |  |
Other IPO Related Expenses | 0.3 | [1] | 1.5 | [1] | 1.2 | [1] | 1.7 | [1] |
IPO and Secondary-offering related expenses | $ 0.3 |  | $ 74.1 |  | $ 1.2 |  | $ 74.3 |  |
[1] | Other expenses include secondary-offering expenses of $0.3 million and $1.2 million for the three and nine months ended September 30, 2014, respectively. There were no secondary-offering expenses recognized during the three and nine months ended September 30, 2013.

X
- Definition Accelerated share based compensation expense and related employer payroll taxes + References No definition available. + Details
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Namespace Prefix: | cdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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 IPO and Secondary-offering related expenses + References No definition available. + Details
Name: | cdw_IPOandSecondaryofferingrelatedexpenses
Namespace Prefix: | cdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | cdw_IPOandSecondaryOfferingRelatedExpensesLineItems
Namespace Prefix: | cdw_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Net proceeds used for Termination of Management Services agreement + References No definition available. + Details
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Namespace Prefix: | cdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Other IPO Related Expenses + References No definition available. + Details
Name: | cdw_OtherIPORelatedExpenses
Namespace Prefix: | cdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration