Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income (loss)	$ 47.7	$ (39.0)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	105.7	102.4
Equity-based compensation expense	11.5	8.1
Deferred income taxes	(32.0)	(17.5)
Allowance for doubtful accounts	0	0.9
Amortization of deferred financing costs and debt premium	8.0	7.7
Net loss on extinguishments of long-term debt	9.4	118.9
Other	0.9	4.2
Changes in assets and liabilities:
Accounts receivable	16.9	(86.1)
Merchandise inventory	0.1	(56.0)
Other assets	(45.3)	(15.6)
Accounts payable-trade	170.5	117.0
Other current liabilities	12.1	(4.3)
Long-term liabilities	(0.8)	(10.9)
Net cash provided by operating activities	304.7	129.8
Cash flows from investing activities:
Capital expenditures	(15.7)	(16.7)
Cash settlements on interest rate swap agreements	0	(6.6)
Premium payments on interest rate cap agreements	0	(3.2)
Net cash used in investing activities	(15.7)	(26.5)
Cash flows from financing activities:
Proceeds from borrowings under revolving credit facility	256.0	755.0
Repayments of borrowings under revolving credit facility	(256.0)	(783.1)
Repayments of senior secured term loan facility	(201.0)	(132.0)
Proceeds from issuance of Senior Notes	135.7	1,175.0
Payments to extinguish Senior Notes	(136.9)	(1,175.0)
Payments of debt financing costs	(2.1)	(26.3)
Net change in accounts payable-inventory financing	(25.5)	89.9
Investment from CDW Holdings LLC	0	1.0
Net cash used in financing activities	(230.1)	(95.7)
Effect of exchange rate changes on cash and cash equivalents	(0.1)	0.4
Net increase in cash and cash equivalents	58.8	8.0
Cash and cash equivalents - beginning of period	99.9	36.6
Cash and cash equivalents - end of period	158.7	44.6
Supplementary disclosure of cash flow information:
Interest paid, net, including cash settlements on interest rate swap agreements	(151.4)	(178.2)
Taxes (paid) refunded, net	(38.4)	35.0
Class B Common Shares [Member]
Cash flows from financing activities:
Repurchase of Class B common shares	$ (0.3)	$ (0.2)