Document and Entity Information Document	3 Months Ended
	Mar. 31, 2013	May 07, 2013 Class A Common Shares [Member]	May 07, 2013 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	Mar. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		100,000	915,309