Document and Entity Information Document	6 Months Ended
	Jun. 30, 2012	Aug. 06, 2012 Class A Common Shares [Member]	Aug. 06, 2012 Class B Common Shares [Member]
Document and Entity Information
Entity Registrant Name	CDW Corp
Entity Central Index Key	0001402057
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 30, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		100,000	913,991