Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net income (loss)	$ 132.8	$ 119.0	$ 17.1
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	208.2	210.2	204.9
Equity-based compensation expense	46.6	22.1	19.5
Deferred income taxes	(48.7)	(56.3)	(10.2)
Allowance for doubtful accounts	0	0	0.4
Amortization of deferred financing costs	8.8	13.6	15.7
Net loss (gain) on extinguishments of long-term debt	64.0	17.2	118.9
Realized loss on interest rate swap agreements	0	0	2.8
Mark to market loss on interest rate derivatives	0.1	0.9	4.2
Net loss (gain) on sale and disposals of assets	0	0.1	0.3
Other	1.6	0	(0.6)
Changes in assets and liabilities:
Accounts receivable	(170.8)	(10.4)	(183.4)
Merchandise inventory	(67.5)	7.1	(29.0)
Other assets	(10.1)	(3.8)	50.3
Accounts payable-trade	146.1	0.8	(19.8)
Other current liabilities	64.1	(2.1)	39.6
Long-term liabilities	(8.9)	(1.0)	(16.0)
Net cash provided by operating activities	366.3	317.4	214.7
Cash flows from investing activities:
Capital expenditures	(47.1)	(41.4)	(45.7)
Cash settlements on interest rate swap agreements	0	0	(6.6)
Premium payments on interest rate cap agreements	0	(0.3)	(3.7)
Net cash used in investing activities	(47.1)	(41.7)	(56.0)
Cash flows from financing activities:
Proceeds from borrowings under revolving credit facility	63.0	289.0	1,295.0
Repayments of borrowings under revolving credit facility	(63.0)	(289.0)	(1,483.2)
Repayments of long-term debt	(51.1)	(201.0)	(132.0)
Proceeds from issuance of long-term debt	1,535.2	135.7	1,175.0
Payments to extinguish long-term debt	(2,047.4)	(243.2)	(1,175.0)
Payments of debt financing costs	(6.1)	(2.1)	(26.3)
Investment from CDW Holdings LLC	0	2.8	1.0
Net change in accounts payable-inventory financing	7.4	(29.5)	250.5
Payment of incentive compensation plan withholding taxes	(24.1)	0	0
Net proceeds from issuance of common shares	424.7	0	0
Repurchase of common shares	(0.2)	(0.7)	(0.4)
Dividends paid	(7.3)	0	0
Excess tax benefits from equity-based compensation	0.6	0	0
Net cash used in financing activities	(168.3)	(338.0)	(95.4)
Effect of exchange rate changes on cash and cash equivalents	(0.7)	0.3	0
Net increase (decrease) in cash and cash equivalents	150.2	(62.0)	63.3
Cash and cash equivalents - beginning of period	37.9	99.9	36.6
Cash and cash equivalents - end of period	188.1	37.9	99.9
Supplementary disclosure of cash flow information:
Interest paid, including cash settlements on interest rate swap agreements	(267.6)	(302.7)	(332.9)
Taxes refunded (paid), net	(82.5)	(123.2)	20.9
Non-cash investing and financing activities:
Capital expenditures accrued in accounts payable-trade	$ 0.2	$ 0.5	$ 1.1