v2.4.1.9
Shareholders' Equity IPO- and secondary-offering related expenses (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2014
Dec. 31, 2013
Class of Stock [Line Items]            
Secondary-offering related expenses $ 0.2cdw_Secondaryofferingrelatedexpenses $ 0.3cdw_Secondaryofferingrelatedexpenses $ 0.5cdw_Secondaryofferingrelatedexpenses $ 0.4cdw_Secondaryofferingrelatedexpenses $ 1.4cdw_Secondaryofferingrelatedexpenses [1] $ 0.6cdw_Secondaryofferingrelatedexpenses
Net proceeds used for termination of management services agreement         0cdw_Netproceedsusedforterminationofmanagementservicesagreement [2] 24.4cdw_Netproceedsusedforterminationofmanagementservicesagreement [2]
Other IPO Related Expenses           2.4cdw_OtherIPORelatedExpenses [1]
IPO and Secondary-offering related expenses           75.0cdw_IPOandSecondaryofferingrelatedexpenses
Accelerated share based compensation expense and related employer payroll taxes         0cdw_Acceleratedsharebasedcompensationexpenseandrelatedemployerpayrolltaxes [3] 40.7cdw_Acceleratedsharebasedcompensationexpenseandrelatedemployerpayrolltaxes [3]
Charge for payment of RDU Plan cash retention pool         0cdw_ChargeforpaymentofRDUPlancashretentionpool [4] 7.5cdw_ChargeforpaymentofRDUPlancashretentionpool [4]
Net proceeds used for termination of Management Services Agreement           $ 24.4cdw_NetproceedsusedforterminationofManagementServicesAgreement
[1] Other expenses include secondary-offering expenses of $1.4 million and $0.6 million for the years ended December 31, 2014 and 2013, respectively.
[2] Represents the payment of a termination fee to affiliates of the Sponsors in connection with the termination of the management services agreement with such entities.
[3] See Note 10 for additional discussion of the impact of the IPO on the Company's equity awards.
[4] See Note 12 for additional discussion of this transaction.