Document and Entity Information Document (USD $)	12 Months Ended
	Dec. 31, 2012	Mar. 06, 2013 Common Class A [Member]	Mar. 06, 2013 Class B Common Shares [Member]
Entity Information [Line Items]
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-K
Document Period End Date	Dec. 31, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Current Reporting Status	No
Entity Voluntary Filers	Yes
Entity Well-known Seasoned Issuer	No
Entity Public Float	$ 0
Entity Common Stock, Shares Outstanding		100,000	914,537