Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2011	Mar. 07, 2012 Common Class A [Member]	Mar. 07, 2012 Common Class B [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, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		100,000	912,706
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	Yes
Entity Current Reporting Status	No
Entity Public Float