Description Of Business And Summary Of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2017
Description of Business and Summary of Significant Accounting Policies [Abstract]
Description of Business, Policy	Description of Business CDW Corporation (“Parent”) is a Fortune 500 company with multi-national capabilities and a leading provider of integrated information technology (“IT”) solutions to small, medium and large business, government, education and healthcare customers in the United States, Canada and the United Kingdom. The Company's offerings range from discrete hardware and software products to integrated IT solutions such as mobility, security, data center optimization, cloud computing, virtualization and collaboration. Throughout this report, the terms the “Company” and “CDW” refer to Parent and its 100% owned subsidiaries. Parent has two 100% owned subsidiaries, CDW LLC and CDW Finance Corporation. CDW LLC is an Illinois limited liability company that, together with its 100% owned subsidiaries, holds all material assets and conducts all business activities and operations of the Company. CDW Finance Corporation is a Delaware corporation formed for the sole purpose of acting as co-issuer of certain debt obligations and does not hold any material assets or engage in any business activities or operations.
Basis of Presentation, Policy	Basis of Presentation The accompanying unaudited interim Consolidated Financial Statements as of March 31, 2017 and for the three months ended March 31, 2017 and 2016 (the “Consolidated Financial Statements”) have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and the rules and regulations of the US Securities and Exchange Commission (the “SEC”) for interim financial statements. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to the rules and regulations of the SEC. These Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2016 (the “December 31, 2016 Consolidated Financial Statements”). The significant accounting policies used in preparing these Consolidated Financial Statements were applied on a basis consistent with those reflected in the December 31, 2016 Consolidated Financial Statements. In the opinion of management, the Consolidated Financial Statements contain all adjustments (consisting of a normal, recurring nature) necessary to present fairly the Company's financial position, results of operations, comprehensive income, cash flows and changes in stockholders' equity as of the dates and for the periods indicated. The unaudited results of operations for such interim periods reported are not necessarily indicative of results for the full year.
Principles of Consolidation, Policy	Principles of Consolidation The accompanying Consolidated Financial Statements include the accounts of Parent and its 100% owned subsidiaries. All intercompany transactions and accounts are eliminated in consolidation.
Use of Estimates, Policy	Use of Estimates The preparation of the Consolidated Financial Statements in accordance with GAAP requires management to make use of certain estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the Consolidated Financial Statements and the reported amounts of revenue and expenses during the reported periods. The Company bases its estimates on historical experience and on various other assumptions that management believes are reasonable under the circumstances, the results of which form the basis for making judgments about carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ from those estimates. The notes to the Consolidated Financial Statements contained in the December 31, 2016 Consolidated Financial Statements include an additional discussion of the significant accounting policies and estimates used in the preparation of the Company's Consolidated Financial Statements. There have been no material changes to the Company's significant accounting policies and estimates during the three months ended March 31, 2017.
Derivatives, Reporting of Derivative Activity [Policy Text Block]	Accounting for Derivative Instruments The Company has entered into interest rate cap agreements for the purpose of hedging its exposure to fluctuations in interest rates. The interest rate cap agreements are designated as cash flow hedges of interest rate risk and recorded at fair value in Other assets on the Consolidated Balance Sheets. The gain or loss on the derivative instruments is reported as a component of Accumulated Other Comprehensive Loss ("AOCL") until reclassified to Interest expense in the same period the hedge transaction affects earnings.