CDW (CDW) 10-Q 3 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	3 Months Ended
	Mar. 31, 2018	Apr. 27, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	CDW Corp
Entity Central Index Key	1,402,057
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		151,759,324

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 221	$ 144.2
Accounts receivable, net of allowance for doubtful accounts of $6.2 for both periods	2,274	2,329.3
Merchandise inventory	485.8	411.5
Miscellaneous receivables	310.2	343
Prepaid expenses and other	188.9	168.3
Total current assets	3,479.9	3,396.3
Property and equipment, net	153.1	161.1
Goodwill	2,488.8	2,479.6
Other intangible assets, net	859	897
Other assets	47.1	32.7
Total Assets	7,027.9	6,966.7
Current liabilities:
Accounts payable-trade	1,288.5	1,317.7
Accounts payable-inventory financing	523.7	498
Current maturities of long-term debt	25.8	25.5
Contract liabilities	193.6	158.8
Accrued expenses and other current liabilities:
Compensation	140.9	129.5
Interest	15.9	21.6
Sales taxes	42	43.8
Advertising	90.5	89.2
Income taxes	56.7	16.2
Other	204.9	221.8
Total current liabilities	2,582.5	2,522.1
Long-term liabilities:
Debt	3,209.7	3,210
Deferred income taxes	188.9	196.3
Other liabilities	49.9	52.7
Total long-term liabilities	3,448.5	3,459
Stockholders' equity:
Preferred stock, $0.01 par value, 100.0 shares authorized, no shares issued or outstanding for both periods	0	0
Common stock, $0.01 par value, 1,000.0 shares authorized; 151.9 and 153.1 shares issued, respectively	1.5	1.5
Less: treasury stock, $0.01 par value, 0.0 and 0.1 shares held, respectively	0	0
Outstanding common stock, $0.01 par value, 151.9 and 153.0 shares outstanding, respectively	1.5	1.5
Paid-in capital	2,928.5	2,911.6
Accumulated deficit	(1,854.6)	(1,831.6)
Accumulated other comprehensive loss	(78.5)	(95.9)
Total stockholders' equity	996.9	982.9
Total stockholders' equity		985.6
Total Liabilities and Stockholders' Equity	$ 7,027.9	$ 6,966.7

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 6.2	$ 6.2
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	100	100
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000	1,000
Common stock, shares issued (in shares)	151.9	153.1
Common stock, shares outstanding (in shares)	151.9	153
Treasury shares, par value (in dollars per share)	$ 0.01	$ 0.01
Treasury stock, shares held (in shares)	0	0.1

Consolidated Statements Of Oper

Consolidated Statements Of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net sales	$ 3,606.4	$ 3,256
Cost of sales	3,002.5	2,702.5
Gross profit	603.9	553.5
Selling and administrative expenses	362.7	347.4
Advertising expense	37.1	35.4
Income from operations	204.1	170.7
Interest expense, net	(37.7)	(39.7)
Net loss on extinguishments of long-term debt	0	(57.4)
Other (expense) income	(0.7)	0.9
Income before income taxes	165.7	74.5
Income tax expense	(38.7)	(16.3)
Net income	$ 127	$ 58.2
Net income per common share:
Basic (in dollars per share)	$ 0.83	$ 0.36
Diluted (in dollars per share)	$ 0.82	$ 0.36
Weighted-average common shares outstanding:
Basic (in shares)	152.2	159.4
Diluted (in shares)	154.8	162.8
Cash dividends declared per common share (in dollars per share)	$ 0.2100	$ 0.1600

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income		$ 127	$ 58.2
Foreign currency translation, net	[1]	14.2	6.5
Unrealized loss from hedge accounting, net	[2]	3.2	(0.4)
Other comprehensive income, net		17.4	6.1
Comprehensive income		144.4	64.3
Tax expense (benefit) on foreign currency translation		(0.1)	0
Tax expense (benefit) on unrealized loss from hedge accounting		$ 1.1	$ (0.3)
[1]	(1) Net of tax benefit of $0.1 million and zero for the three months ended March 31, 2018 and 2017, respectively.
[2]	(2) Net of tax expense of $1.1 million and a tax benefit of $0.3 million for the three months ended March 31, 2018 and 2017, respectively.

Consolidated Statement of Share

Consolidated Statement of Shareholders' Equity (Unaudited) - 3 months ended Mar. 31, 2018 - USD ($) shares in Millions, $ in Millions	Total		Preferred Stock	Common Stock	Treasury Stock	Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2017			0	153.1	0.1
Beginning balance at Dec. 31, 2017	$ 982.9		$ 0	$ 1.5	$ 0	$ 2,911.6	$ (1,834.3)	$ (95.9)
Cumulative adjustment upon adoption of ASC 606 at Dec. 31, 2017	2.7						2.7
Balance as of December 31, 2017 (as adjusted) at Dec. 31, 2017	985.6		$ 0	$ 1.5	$ 0	2,911.6	(1,831.6)	(95.9)
Shareholders' Equity (Deficit) [Roll Forward]
Net income	127						127
Equity-based compensation expense	7.1					7.1
Stock option exercises (in shares)				0.3
Stock option exercises	7.3					7.3
Coworker Stock Purchase Plan	2.4					2.4
Repurchases of common stock (in shares)				(1.5)
Repurchases of common stock	(109.2)						(109.2)
Dividends paid	(32)					0.1	(32.1)
Incentive compensation plan shares withheld for taxes (in shares)					(0.1)
Incentive compensation plan shares withheld for taxes	(8.7)						(8.7)
Foreign currency translation	14.2	[1]						14.2
Unrealized gain from hedge accounting	3.2							3.2
Ending balance (in shares) at Mar. 31, 2018			0	151.9	0
Ending balance at Mar. 31, 2018	$ 996.9		$ 0	$ 1.5	$ 0	$ 2,928.5	$ (1,854.6)	$ (78.5)
[1]	(1) Net of tax benefit of $0.1 million and zero for the three months ended March 31, 2018 and 2017, respectively.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 127	$ 58.2
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	66.6	64.2
Equity-based compensation expense	8.1	12.1
Deferred income taxes	(13.4)	(19.1)
Amortization of deferred financing fees, debt premium and debt discount, net	1.2	3.2
Net loss on extinguishments of long-term debt	0	57.4
Mark-to-market gain on interest rate cap agreements	0	(0.5)
Other	(0.1)	2.1
Changes in assets and liabilities:
Accounts receivable	60.5	184.7
Merchandise inventory	(72.4)	(36)
Other assets	15.4	(20)
Accounts payable-trade	(29.8)	(10.4)
Other current liabilities	59.5	78.7
Long-term liabilities	(0.4)	(4.7)
Net cash provided by operating activities	222.2	369.9
Cash flows used in investing activities:
Capital expenditures	(15.9)	(19.6)
Net cash used in investing activities	(15.9)	(19.6)
Cash flows used in financing activities:
Proceeds from borrowings under revolving credit facilities	170	44.1
Repayments of borrowings under revolving credit facilities	(170)	(6.1)
Repayments of long-term debt	(3.7)	(3.7)
Proceeds from issuance of long-term debt	0	2,083
Payments to extinguish long-term debt	0	(2,121.3)
Payments of debt financing fees	0	(9.6)
Net change in accounts payable-inventory financing	24.9	(135.7)
Premium payments on interest rate cap agreements	(12.6)	0
Proceeds from stock option exercises	7.3	4.4
Proceeds from Coworker Stock Purchase Plan	2.4	2.1
Repurchases of common stock	(109.2)	(175.4)
Payment of incentive compensation plan withholding taxes	(8.7)	(18.3)
Dividends	(32)	(25.5)
Other	0.4	(0.2)
Net cash used in financing activities	(131.2)	(362.2)
Effect of exchange rate changes on cash and cash equivalents	1.7	(0.1)
Net increase (decrease) in cash and cash equivalents	76.8	(12)
Cash and cash equivalents—beginning of period	144.2	263.7
Cash and cash equivalents—end of period	221	251.7
Supplementary disclosure of cash flow information:
Interest paid	(42.7)	(48.4)
Taxes paid, net	$ (10.6)	$ (6.3)

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Description of Business and Summary of Significant Accounting Policies	Description of Business and Summary of Significant Accounting Policies 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 ("US"), the United Kingdom ("UK") and Canada. 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 as described in Note 12 (Supplemental Guarantor Information) and does not hold any material assets or engage in any business activities or operations. Basis of Presentation The accompanying unaudited interim Consolidated Financial Statements as of March 31, 2018 and for the three months ended March 31, 2018 and 2017 (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 and the notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 (the " December 31, 2017 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, 2017 Consolidated Financial Statements except for changes from the adoption of Accounting Standards Update ("ASU") 2014-09, Revenue from Contracts with Customers, as amended ("Topic 606"), as discussed below. 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. Effective January 1, 2018, the Company adopted the requirements of Topic 606 utilizing the full retrospective method as discussed in Note 2 (Recent Accounting Pronouncements) . Prior period amounts have been adjusted accordingly. 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 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, 2017 Consolidated Financial Statements include a discussion of the significant accounting policies and estimates used in the preparation of the Company's Consolidated Financial Statements. Except as noted above for the adoption of Topic 606, there have been no material changes to the Company's significant accounting policies and estimates during the three months ended March 31, 2018 . Revenue Recognition The Company is a primary distribution channel for a large group of vendors and suppliers, including original equipment manufacturers ("OEMs"), software publishers and wholesale distributors. The Company accounts for a contract when it has approval and commitment from both parties, the rights of the parties are identified, payment terms are established, the contract has commercial substance and collectability of consideration is probable. The Company considers the following indicators amongst others when determining whether it is acting as a principal in the transaction and recording revenue on a gross basis: (i) the Company is primarily responsible for fulfilling the promise to provide the specified goods or service, (ii) the Company has inventory risk before the specified good or service has been transferred to a customer or after transfer of control to the customer and (iii) the Company has discretion in establishing the price for the specified good or service. If a transaction does not meet the Company's indicators of being a principal in the transaction, then the Company is acting as an agent in the transaction and the associated revenues are recognized on a net basis. The Company recognizes revenue once control has passed to the customer. The following indicators are evaluated in determining when control has passed to the customer: (i) the Company has a right to payment for the product or service, (ii) the customer has legal title to the product, (iii) the Company has transferred physical possession of the product to the customer, (iv) the customer has the significant risk and rewards of ownership of the product and (v) the customer has accepted the product. The Company's products can be delivered to customers in a variety of ways, including (i) as physical product shipped from the Company's warehouse, (ii) via drop-shipment by the vendor or supplier or (iii) via electronic delivery of keys for software licenses. The Company’s shipping terms typically specify F.O.B. destination. The Company leverages drop-shipment arrangements with many of its vendors and suppliers to deliver products to its customers without having to physically hold the inventory at its warehouses. The Company is the principal in the transaction and recognizes revenue for drop-shipment arrangements on a gross basis. Revenue Recognition for Hardware Revenues from sales of hardware products are recognized on a gross basis as the Company is acting as a principal in these transactions, with the selling price to the customer recorded as Net sales and the acquisition cost of the product recorded as Cost of sales. The Company recognizes revenue from these transactions when control has passed to the customer, which is usually upon delivery of the product to the customer. In some instances, the customer agrees to buy the product from the Company but requests delivery at a later date, commonly known as bill-and-hold arrangements. For these transactions, the Company deems that control passes to the customer when the product is ready for delivery. The Company views products ready for delivery when the customer has a signed agreement, significant risk and rewards for the products, the ability to direct the assets, the products have been set aside specifically for the customer, cannot be redirected to another customer and for customer orders that include configuration services, when such services have been completed. Revenue Recognition for Software Revenues from most software license sales are recognized as a single performance obligation on a gross basis as the Company is acting as a principal in these transactions at the point the software license is delivered to the customer. Generally, software licenses are sold with accompanying third-party delivered software assurance, which is a product that allows customers to upgrade, at no additional cost, to the latest technology if new capabilities are introduced during the period that the software assurance is in effect. The Company evaluates whether the software assurance is a separate performance obligation by assessing if the third-party delivered software assurance is critical or essential to the core functionality of the software itself. This involves considering if the software provides its original intended functionality to the customer without the updates, if the customer would ascribe a higher value to the upgrades versus the up-front deliverable, if the customer would expect frequent intelligence updates to the software (such as updates that maintain the original functionality), and if the customer chooses to not delay or always install upgrades. If the Company determines that the accompanying third-party delivered software assurance is critical or essential to the core functionality of the software license, the software license and the accompanying third-party delivered software assurance are recognized as a single performance obligation. The value of the product is primarily the accompanying support delivered by a third-party and therefore the Company is acting as an agent in these transactions and recognizes them on a net basis at the point the associated software license is delivered to the customer. For software licenses where the accompanying third-party delivered software assurance is not critical or essential to the core functionality, the software assurance is recognized as a separate performance obligation, with the associated revenue recognized on a net basis at the point the related software license is delivered to the customer. For additional details regarding the accounting for bundled arrangements, see "Revenue Recognition for Bundled Arrangements" below. The Company's vendor partners warrant most of the products the Company sells. These manufacturer warranties are assurance-type warranties and are not considered separate performance obligations. The warranties are not sold separately and only provide assurance that products will conform with the manufacturer's specifications. In some transactions, a third-party will provide the customer with an extended warranty. These extended warranties are sold separately and provide the customer with a service in addition to assurance that the product will function as expected. The Company considers these service-type warranties to be separate performance obligations from the underlying product. For service-type warranties, the Company is arranging for those services to be provided by the third-party and therefore is acting as an agent in the transaction and records revenue on a net basis at the point of sale. Revenue Recognition for Services The Company provides professional services, which include project managers and consultants recommending, designing and implementing IT solutions. Revenue from professional services is recognized either on a time and materials basis or recognized proportionally as costs are incurred for fixed fee project work. For time and materials projects, revenue is recognized on a gross basis each month as work is performed and the Company transfers those services. The Company sells cloud computing solutions, which include Software as a Service ("SaaS") and Infrastructure as a Service ("IaaS"). SaaS solutions utilize third-party partners to offer the Company's customers access to software in the cloud that enhances office productivity, provides security or assists in collaboration. IaaS solutions utilize third-party partners to enable customers to access data center functionality in a cloud-based solution, including storage, computing and networking. The Company recognizes revenue for cloud computing solutions for arrangements with one-time invoicing to the customer at the time of invoice on a net basis as the Company is acting as an agent in the transaction. For subscription-based arrangements with monthly billing, the Company is acting as an agent in the transaction and recognizes revenue as it invoices the customer for its monthly usage on a net basis. Revenues from the sale of data center services, such as managed and remote managed services, server co-location, internet connectivity and data backup and storage provided by the Company, are recognized over the period the service is provided. Most hosting and managed service obligations are based on the quantity and pricing parameters established in the agreement. As the customer receives the benefit of service each month, the Company recognizes the respective revenue on a gross basis as the Company is acting as a principal in the transaction. Additionally, the Company's managed services team provides project support to customers that are billed on a fixed fee basis. The Company is acting as the principal in the transaction and recognizes revenue on a gross basis based on the total number of hours incurred for the period over the total expected hours for the project. Total expected hours to complete the project is updated for each period and best represents the transfer of control of the service to the customer. The Company's customers are offered the opportunity by certain of its vendors to purchase software licenses and software assurance under enterprise agreements ("EAs"), referred to as services in this paragraph. For most EA transactions, the Company's obligation to the customer is that of a distributor or sales agent of the services, where all obligations for providing the services to customers are passed to the Company's vendors. The Company's performance obligations are satisfied at the time of the sale. In other EA transactions, the Company is responsible for fulfilling the promised services to the customer and providing remedy or refund for work if the customer is not satisfied with the delivered services, has inventory risk in the arrangement and has full control to set the price for the customer. This results in the Company acting as a principal in the agreement. With most EAs, the Company's vendors will transfer the license and invoice the customer directly, paying resellers an agency fee or commission on these sales. The Company records these fees as a component of Net sales as earned and there is no corresponding Cost of sales amount. Revenue Recognition for Bundled Arrangements The Company also sells some of its products and services as part of bundled contract arrangements containing multiple deliverables, which may include a combination of products and services. For each deliverable that represents a distinct performance obligation, total arrangement consideration is allocated based upon the standalone selling prices of each performance obligation. The Company excludes amounts collected on behalf of third-parties, such as sales taxes, when determining the transaction price. For certain performance obligations, the Company will use a combination of methods to estimate the standalone selling price. When evidence from recent transactions is not available to confirm that the prices are representative of the standalone selling price, an expected cost plus a margin approach is used. Sales In-Transit The Company performs an analysis of the estimated number of days of sales in-transit to customers at the end of each reporting period based on a weighted-average analysis of commercial delivery terms that include drop-shipment arrangements. This analysis is the basis upon which the Company estimates the amount of Net sales in-transit at the end of the period and adjusts revenue and the related costs to reflect only what has been delivered to the customer. Changes in delivery patterns may result in a different number of business days estimated to make this adjustment. Freight Costs The Company records freight billed to its customers as Net sales and the related freight costs as a Cost of sales when product is shipped to the customer. For freight not billed to its customers, the Company records the freight costs as a Cost of sales. The Company's typical shipping terms are F.O.B destination, which results in shipping being performed before the customer obtains control of the product. The Company considers shipping to be a fulfillment activity and not a separate performance obligation. Other The nature of the Company's contracts give rise to variable consideration in the form of sales returns and allowances. The Company estimates variable consideration at the most likely amount to which it is expected to be entitled. This estimated amount is included in the transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. The estimates of variable consideration and determination of whether to include estimated amounts in the transaction price are based on an assessment of the Company's anticipated performance and all information that is reasonably available. At the time of sale, the Company records an estimate for sales returns and allowances and an associated right of return asset based on historical experience. When a contract results in revenue being recognized in excess of the amount the Company has the right to invoice to the customer, a contract asset is recorded on the balance sheet. Contract assets are comprised primarily of professional services with fixed fee arrangements. Contract liabilities consist of payments received from customers, or such consideration that is contractually due, in advance of providing the product or performing services. Contract liabilities are comprised primarily of professional services with fixed fee arrangements, bill-and-hold transactions where control has not passed to the customer and certain governmental contracts. Trade accounts receivable are recorded at the point of sale (or in accordance with the Statement of Work for services) for the total amount payable by the customer to the Company for sale of goods. Taxes to be collected from the customer as part of the sale are included in Accounts receivable trade. Any incremental direct costs of obtaining a contract are deferred on the Consolidated Balance Sheets and amortized over the period of contract performance. The Company typically does not enter into long-term contracts. The Company has elected to use the practical expedient for its performance obligations table to show only those contracts that are longer than 12 months at the time of contract inception and those contracts that are non-cancelable. Additionally, for certain governmental contracts where there are annual renewals, the Company has excluded these contracts since there is only a one-year legal obligation. Typically, the only contracts that are longer than 12 months in duration are related to the Company's professional and managed services business. The Company requests payments for its products and services at the point of sale. The Company generally does not enter into any long-term financing arrangements or payment plans with customers or contracts with customers that have non-cash consideration.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting for Hedging Activities In August 2017, the Financial Accounting Standards Board (the "FASB") issued ASU 2017-12, Derivatives and Hedging (Topic 815), intending to improve the transparency of information included in the financial statements by aligning cash flow and fair value hedge accounting with its risk management activities. The ASU eliminates the requirement to separately measure and report hedge ineffectiveness for cash flow hedges and net investment hedges, and generally requires the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. The ASU also simplifies certain documentation and assessment requirements, and will incorporate new disclosure requirements and amendments to existing disclosures. This ASU is effective for the Company beginning the first quarter of 2019 and allows for early adoption. The Company is currently evaluating the impact the ASU will have on its Consolidated Financial Statements. Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This ASU introduces a new forward-looking approach, based on expected losses, to estimate credit losses on certain types of financial instruments, including trade receivables. The estimate of expected credit losses will require considerations of historical information, current information and reasonable and supportable forecasts. This ASU also expands the disclosure requirements to enable users of financial statements to understand the assumptions, models and methods for estimating expected credit losses. This ASU is effective for the Company beginning in the first quarter of 2020 and allows for early adoption beginning in the first quarter of 2019. The Company is currently evaluating the impact the ASU will have on its Consolidated Financial Statements. Accounting for Leases In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), requiring lessees to recognize assets and liabilities on the balance sheet for the rights and obligations created by long-term leases and to disclose additional quantitative and qualitative information about leasing arrangements. This ASU is effective for the Company beginning in the first quarter of 2019 and allows for early adoption. Although the Company is currently evaluating the provisions of the ASU to determine how it will be affected, the primary impact to the Company of the new ASU will be to record assets and liabilities for current operating leases, which are principally related to the Company's real estate portfolio. Revenue Recognition On January 1, 2018, the Company adopted Topic 606 and utilized the full retrospective method. For additional details, see Note 1 (Description of Business and Summary of Significant Accounting Policies) . For the three months ended March 31, 2017 , the adoption of Topic 606 impacted the Company's results as follows: March 31, 2017 (in millions) (except per share amounts) As Reported New Revenue Standard Adjustment As Adjusted Net sales $ 3,324.7 $ (68.7 ) $ 3,256.0 Gross profit 552.6 0.9 553.5 Gross profit margin 16.6 % 40 bps 17.0 % Income from operations 169.8 0.9 170.7 Income tax expense (16.0 ) (0.3 ) (16.3 ) Net income $ 57.6 $ 0.6 $ 58.2 Net income per common share Basic $ 0.36 $ — $ 0.36 Diluted $ 0.35 $ 0.01 $ 0.36 The adoption of Topic 606 impacted the Company's Consolidated Balance Sheet as of December 31, 2017 as follows: December 31, 2017 (in millions) As Reported New Revenue Standard Adjustment As Adjusted (1) Accounts receivable $ 2,320.5 $ 8.8 $ 2,329.3 Merchandise inventory 449.5 (38.0 ) 411.5 Miscellaneous receivables 336.5 6.5 343.0 Prepaid expenses and other 127.4 40.9 168.3 Total current assets 3,378.1 18.2 3,396.3 Other assets 40.8 (8.1 ) 32.7 Total assets 6,956.6 10.1 6,966.7 Contract liabilities 194.0 (35.2 ) 158.8 Income tax payable 15.1 1.1 16.2 Other accrued expenses 180.2 41.6 221.8 Total current liabilities 2,514.6 7.5 2,522.1 Total liabilities 5,973.7 7.5 5,981.1 Total stockholders’ equity $ 982.9 $ 2.7 $ 985.6 (1) Amounts may not cross-foot due to rounding.

Inventory Financing Agreements

Inventory Financing Agreements	3 Months Ended
	Mar. 31, 2018
Inventory Financing Agreements [Abstract]
Inventory Financing Agreements	Inventory Financing Agreements The Company has entered into agreements with certain financial intermediaries to facilitate the purchase of inventory from various suppliers under certain terms and conditions, as described below. These amounts are classified separately as Accounts payable-inventory financing on the Consolidated Balance Sheets. The Company does not incur any interest expense associated with these agreements as balances are paid when they are due. Amounts included in Accounts payable-inventory financing are as follows: (in millions) March 31, 2018 December 31, 2017 Revolving Loan inventory financing agreement (1) $ 481.6 $ 480.9 Other inventory financing agreements 42.1 17.1 Accounts payable-inventory financing $ 523.7 $ 498.0 (1) The Senior Secured Asset-Based Revolving Credit Facility includes an inventory floorplan sub-facility that enables the Company to maintain an inventory financing agreement with a financial intermediary to facilitate the purchase of inventory from certain vendors on more favorable terms than offered directly by the vendors.

Contract Liabilities and Remain

Contract Liabilities and Remaining Performance Obligations	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract Liabilities and Remaining Performance Obligations	Contract Liabilities and Remaining Performance Obligations The Company's contract liabilities consist of payments received from customers, or such consideration that is contractually due, in advance of providing the product or performing services. The Company's contract liabilities are reported in a net position on a contract-by-contract basis at the end of each reporting period. As of March 31, 2018 and December 31, 2017 , the contract liability balance was $194 million and $159 million , respectively. During the three months ended March 31, 2018 and 2017 , the Company recognized revenue of $58 million and $45 million , respectively, related to its contract liabilities. A contract's transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. For more information regarding the Company's performance obligations, see Note 1 (Description of Business and Summary of Significant Accounting Policies) . The following table represents the total transaction price for the remaining performance obligations as of March 31, 2018 related to non-cancelable contracts longer than 12 months in duration that is expected to be recognized over future periods. (in millions) Within 1 Year Years 1-2 Years 2-3 Thereafter Remaining Performance Obligations $ 39.2 $ 25.6 $ 9.6 $ 0.7

Financial Instruments

Financial Instruments	3 Months Ended
	Mar. 31, 2018
Financial Instruments [Abstract]
Financial Instruments	Financial Instruments The Company's indebtedness creates interest rate risk on its variable-rate debt. The Company uses derivative financial instruments to manage its exposure to interest rate risk. The Company does not hold or issue derivative financial instruments for trading or speculative purposes. The Company has interest rate cap agreements that entitle it to payments from the counterparty of the amount, if any, by which three-month LIBOR exceeds the strike rates of the caps during the agreement period in exchange for an upfront premium. During the first quarter of 2018, the Company entered into interest rate cap agreements with a combined notional value of $1.4 billion resulting in premiums paid to the counterparties of $13 million . As of March 31, 2018 and December 31, 2017 , the Company had the following interest rate cap agreements for which the fair values are classified within Other assets on the Consolidated Balance Sheets: March 31, 2018 December 31, 2017 Notional Value (in millions) Effective Date Maturity Date Fair Value (in millions) Fair Value (in millions) $ 1,400.0 January 17, 2017 December 31, 2018 $ 8.8 $ 5.4 1,400.0 December 31, 2018 December 31, 2020 12.7 — $ 21.5 $ 5.4 The fair value of the Company's interest rate cap agreements is classified as Level 2 in the fair value hierarchy. The valuation of the interest rate cap agreements is derived by using a discounted cash flow analysis on the expected cash receipts that would occur if variable interest rates rise above the strike rates of the caps. This analysis reflects the contractual terms of the interest rate cap agreements, including the period to maturity, and uses observable market-based inputs, including LIBOR curves and implied volatilities. The Company also incorporates insignificant credit valuation adjustments to appropriately reflect the respective counterparty's nonperformance risk in the fair value measurements. The counterparty credit spreads are based on publicly available credit information obtained from a third-party credit data provider. For additional details, see Note 6 (Long-Term Debt) . The interest rate cap agreements are designated as cash flow hedges. The effective portion of changes in the fair value of derivatives that qualify as cash flow hedges is recorded in Accumulated other comprehensive loss and is subsequently reclassified into Interest expense in the period when the hedged forecasted transaction affects earnings. If a derivative is deemed to be ineffective, the ineffective portion of the change in fair value of the derivative is recognized directly into earnings. The Company's interest rate cap agreements were deemed effective during both the three months ended March 31, 2018 and 2017 , and the Company expects the derivatives will continue to be effective for the next twelve months. The Company recorded a $3 million gain, net of a $1 million tax expense, for the effective portion of the interest rate cap agreements into Accumulated other comprehensive loss for the three months ended March 31, 2018 . During the three months ended March 31, 2017 , the Company recorded an insignificant loss for the effective portion of the interest rate cap agreements into Accumulated other comprehensive loss. During the three months ended March 31, 2018 , the Company reclassified less than $1 million from Accumulated other comprehensive loss to earnings within Interest expense, net on the Consolidated Statement of Operations. The Company expects to reclassify $5 million from Accumulated other comprehensive loss into Interest expense, net during the next twelve months. Prior to the election of hedge accounting treatment, the Company recognized less than $1 million of Interest income during the three months ended March 31, 2017 in the Company's Consolidated Statement of Operations related to the changes in the fair value of the interest rate cap agreements.

Long-Term Debt

Long-Term Debt	3 Months Ended
	Mar. 31, 2018
Long-term Debt, Unclassified [Abstract]
Long-Term Debt	Long-Term Debt Long-term debt as of March 31, 2018 is as follows: (dollars in millions) Interest Rate Principal Unamortized Discount and Deferred Financing Fees Total Senior secured asset-based revolving credit facility — % $ — $ — $ — CDW UK revolving credit facility — % — — — Senior secured term loan facility (1) 4.3 % 1,464.3 (2.0 ) 1,462.3 CDW UK term loan 2.0 % 78.5 (1.3 ) 77.2 Senior notes due 2023 5.0 % 525.0 (4.2 ) 520.8 Senior notes due 2024 5.5 % 575.0 (5.0 ) 570.0 Senior notes due 2025 5.0 % 600.0 (7.0 ) 593.0 Other long-term obligations 12.2 — 12.2 Total debt 3,255.0 (19.5 ) 3,235.5 Less current maturities (25.8 ) — (25.8 ) Long-term debt, excluding current maturities $ 3,229.2 $ (19.5 ) $ 3,209.7 (1) The Senior secured term loan facility has a variable interest rate, which has effectively been capped through the use of an interest rate cap (see Note 5 (Financial Instruments) ). The interest rate disclosed represents the variable interest rate in effect as of March 31, 2018 . Long-term debt as of December 31, 2017 is as follows: (dollars in millions) Interest Principal Unamortized Discount and Deferred Financing Fees Total Senior secured asset-based revolving credit facility — % $ — $ — $ — CDW UK revolving credit facility — % — — — Senior secured term loan facility (1) 3.7 % 1,468.0 (2.0 ) 1,466.0 CDW UK term loan 1.9 % 75.7 (1.4 ) 74.3 Senior notes due 2023 5.0 % 525.0 (4.5 ) 520.5 Senior notes due 2024 5.5 % 575.0 (5.2 ) 569.8 Senior notes due 2025 5.0 % 600.0 (7.3 ) 592.7 Other long-term obligations 12.2 — 12.2 Total debt 3,255.9 (20.4 ) 3,235.5 Less current maturities (25.5 ) — (25.5 ) Long-term debt, excluding current maturities $ 3,230.4 $ (20.4 ) $ 3,210.0 (1) The Senior secured term loan facility has a variable interest rate, which has effectively been capped through the use of an interest rate cap (see Note 5 (Financial Instruments) ). The interest rate disclosed represents the variable interest rate in effect as of December 31, 2017 . Senior Secured Asset-based Revolving Credit Facility ("Revolving Loan") As of March 31, 2018 , the Company had no outstanding borrowings under the Revolving Loan, less than $1 million of undrawn letters of credit, $462 million reserved for the floorplan sub-facility and a borrowing base of $1.6 billion , which is based on the amount of eligible inventory and accounts receivable balances as of February 28, 2018. Borrowings under the Revolving Loan are limited by the borrowing base. As of March 31, 2018 , the Company could have borrowed up to an additional $987 million under the Revolving Loan. Borrowings are also limited by a minimum liquidity condition, which provides that, if excess cash availability is less than the lower of (i) $125 million and (ii) the greater of (a) 10.0% of the borrowing base, and (b) $100 million , the lenders are not required to lend additional amounts under the Revolving Loan unless the consolidated fixed charge coverage ratio, as defined, is at least 1.00 to 1.00 . Borrowings under the Revolving Loan bear interest at a variable interest rate plus an applicable margin. The interest rate margin is based on one of two indices, either (i) LIBOR or (ii) the Alternate Base Rate ("ABR"), with the ABR being the greater of (a) the prime rate, (b) the federal funds effective rate plus 50 basis points or (c) the one-month LIBOR plus 1.00% . The applicable margin varies ( 1.25% to 1.75% for LIBOR borrowings and 0.25% to 0.75% for ABR borrowings) depending upon average daily excess cash availability under the agreement evidencing the Revolving Loan. During the three months ended March 31, 2017 , the Company amended, extended and increased its Revolving Loan and recorded a loss on extinguishment of long-term debt of $1 million in the Consolidated Statement of Operations, representing a write-off of a portion of unamortized deferred financing fees. Fees of $4 million related to the Revolving Loan were capitalized as deferred financing fees and are being amortized over the five-year term of the facility on a straight-line basis. These deferred financing fees are recorded in the Other assets line on the Consolidated Balance Sheets. Senior Secured Term Loan Facility ("Term Loan") As of March 31, 2018 , the outstanding principal amount of the Term Loan was $1.5 billion , excluding $ 2 million of deferred financing fees. Borrowings under the Term Loan bear interest at either (i) the ABR plus a margin or (ii) LIBOR plus a margin, payable quarterly on the last day of each March, June, September and December. The margin is based upon a net leverage ratio as defined in the agreement governing the Term Loan, which is 1.00% for ABR borrowings and 2.00% for LIBOR borrowings as of March 31, 2018 . The Company is required to pay quarterly principal installments of $4 million with the remaining principal amount payable on the maturity date of August 17, 2023 . During the three months ended March 31, 2017 , the Company amended its prior $1.5 billion senior secured term loan facility ("Prior Term Loan Facility") and recorded a loss on extinguishment of long-term debt of $14 million in the Consolidated Statement of Operations. This loss represented the write-off of a portion of the unamortized deferred financing fees of $5 million and unamortized discount related to the Prior Term Loan Facility of $9 million . In connection with the issuance of the Term Loan, the Company incurred and recorded $2 million in deferred financing fees. CDW UK Term Loan As of March 31, 2018 , the outstanding principal amount of the CDW UK Term Loan facility ("CDW UK Term Loan") was £ 56 million ( $79 million at March 31, 2018 ), excluding £ 1 million ($ 1 million at March 31, 2018 ) of deferred financing fees. Commencing during the quarter ending September 30, 2018, the Company is required to make annual principal installments of £ 5 million ( $7 million at March 31, 2018 ), with the remaining principal amount payable on the maturity date of August 1, 2021. Borrowings under the CDW UK Term Loan bear interest at LIBOR plus a margin, payable quarterly on the last day of each March, June, September and December. As of March 31, 2018 , an interest rate of 1.98% was in effect, which represents LIBOR plus a 1.40% margin. The CDW UK Term Loan also includes a separate £ 50 million ( $70 million at March 31, 2018 ) revolving credit facility (the "CDW UK Revolving Credit Facility"). As of March 31, 2018 , the Company had no outstanding borrowings under the CDW UK Revolving Credit Facility. 5.0% Senior Notes due 2023 ("2023 Senior Notes") As of March 31, 2018 , the outstanding principal amount of the 2023 Senior Notes was $525 million . The 2023 Notes will mature on September 1, 2023 and bear interest at a rate of 5.0% per annum, payable semi-annually on March 1 and September 1 of each year. 5.5% Senior Notes due 2024 ("2024 Senior Notes") As of March 31, 2018 , the outstanding principal amount of the 2024 Senior Notes was $575 million . The 2024 Senior Notes will mature on December 1, 2024 and bear interest at a rate of 5.5% per annum, payable semi-annually on June 1 and December 1 of each year. 5.0% Senior Notes due 2025 ("2025 Senior Notes") As of March 31, 2018 , the outstanding principal amount of the 2025 Senior Notes was $600 million . The 2025 Senior Notes will mature on September 1, 2025 and bear interest at a rate of 5.0% per annum, payable semi-annually on March 1 and September 1 of each year. During the three months ended March 31, 2017, the Company completed the issuance of the 2025 Senior Notes at par. The proceeds from the issuance of the 2025 Senior Notes along with cash on hand and proceeds from Revolving Loan borrowings were deposited to redeem all of the then remaining $600 million aggregate principal amount of the 2022 Senior Notes ("2022 Senior Notes"). In connection with this redemption, the Company recorded a loss on extinguishment of long-term debt of $43 million in the Consolidated Statement of Operations for the three months ended March 31, 2017. This loss represents $37 million in redemption premium and $6 million for the write-off of the remaining deferred financing fees related to the 2022 Senior Notes. Debt Guarantors, Covenants and Restrictions CDW LLC is the borrower under the Term Loan and Revolving Loan. CDW LLC and CDW Finance Corporation are the co-issuers of the 2023, 2024 and 2025 Senior Notes ("Senior Notes"). The obligations under the Term Loan, the Revolving Loan and the Senior Notes are guaranteed by Parent and each of CDW LLC's direct and indirect, wholly owned, US subsidiaries (the "Guarantors"). The Revolving Loan is collateralized by a first priority interest in inventory (excluding inventory collateralized under the inventory floorplan arrangements as described in Note 3 (Inventory Financing Agreements) ), deposits and accounts receivable and by a second priority interest in substantially all US assets. The Term Loan is collateralized by a second priority interest in substantially all inventory (excluding inventory collateralized under the inventory floorplan arrangements as described in Note 3 (Inventory Financing Agreements) ), deposits and accounts receivable and by a first priority interest in substantially all other US assets. As of March 31, 2018 , the Company remained in compliance with the covenants under its various credit agreements. The Term Loan contains negative covenants that, among other things, place restrictions and limitations on the ability of the Guarantors to dispose of assets, incur additional indebtedness, incur guarantee obligations, prepay other indebtedness, make distributions or other restricted payments, create liens, make equity or debt investments, make acquisitions, engage in mergers or consolidations or engage in certain transactions with affiliates. As of March 31, 2018 , the amount of CDW's restricted payment capacity under the Term Loan was $1.2 billion . However, the Company is separately permitted to make restricted payments, so long as the total net leverage ratio is less than 3.25 :1.00 on a pro forma basis. The total net leverage ratio was 2.49 :1.00 as of March 31, 2018 . Each of the Senior Notes indentures contain negative covenants that, among other things, place restrictions and limitations on the ability of the Guarantors to enter into sale and lease-back transactions, incur additional secured indebtedness and create liens. The indenture governing each of the Senior Notes do not contain any financial covenants. The CDW UK Term Loan imposes restrictions on CDW UK's ability to transfer funds to the Company through the payment of dividends, repayment of intercompany loans, advances or subordinated debt that require, among other things, the maintenance of a minimum net leverage ratio. As of March 31, 2018 , the amount of restricted payment capacity under the CDW UK Term Loan was £ 99 million ( $139 million at March 31, 2018 ). Fair Value The fair values of the Senior Notes were estimated using quoted market prices for identical liabilities that are traded in over-the-counter secondary markets that are not considered active. The fair value of the Term Loan was estimated using dealer quotes for identical liabilities in markets that are not considered active. The Senior Notes, Term Loan and the CDW UK Term Loan are classified as Level 2 within the fair value hierarchy. The carrying value of the Revolving Loan and the CDW UK Revolving Credit Facility approximate fair value if there are outstanding borrowings. As of March 31, 2018 , the carrying value of the CDW UK Term Loan approximated fair value. The approximate fair values and related carrying values of the Company's long-term debt, including current maturities and excluding unamortized discount and unamortized deferred financing fees, were as follows: (in millions) March 31, 2018 December 31, 2017 Fair value $ 3,290.7 $ 3,366.5 Carrying value 3,255.0 3,255.9

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes On December 22, 2017, the Tax Cuts and Jobs Act was enacted into law. The Tax Cuts and Jobs Act changes several aspects of US federal tax law including: reducing the US corporate income tax rate from 35.0% to 21.0% beginning on January 1, 2018; a one-time tax on the deemed mandatory repatriation of the Company's unremitted foreign earnings which have not been subject to US tax; imposing a minimum US tax on foreign earnings; providing for the immediate expensing of certain qualified property; and changing the tax treatment of performance-based executive compensation and certain employee fringe benefits. The SEC issued Staff Accounting Bulletin 118 allowing for provisional amounts to be recorded during a measurement period not to exceed one year. The Company recorded during the year ending December 31, 2017 provisional amounts for the impact of revaluing deferred tax assets and liabilities, the deemed mandatory repatriation tax on the Company's unremitted foreign earnings and the state income tax effects from the change in federal tax law during the year ended December 31, 2017. The Company did not adjust any of the provisional amounts during the three months ended March 31, 2018. The Company continues to analyze the income tax effects of the Tax Cuts and Jobs Act, as well as monitor guidance from the Internal Revenue Service, US Treasury Department and state taxing authorities and will adjust the provisional amounts within the one-year measurement period. Income tax expense was $39 million for the three months ended March 31, 2018 , compared to $16 million for the same period of the prior year. The effective income tax rate, expressed by calculating the income tax expense as a percentage of Income before income taxes, was 23.4% for the three months ended March 31, 2018 and differed from the US federal statutory rate of 21.0% primarily due to state income taxes offset by excess tax benefits on equity-based compensation. The effective tax rate for the same period of the prior year was 21.9% and differed from the US federal statutory rate of 35.0% primarily due to excess tax benefits on equity-based compensation.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity On February 14, 2018 , the Company retired 109,207 shares of its treasury stock. On December 31, 2017 the shares were acquired in satisfaction of withholding taxes which were paid by the Company on behalf of coworkers under the Performance Share Awards program.

Earnings per Share

Earnings per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share The numerator for both basic and diluted earnings per share is Net income. The denominator for basic earnings per share is the weighted-average shares outstanding during the period. A reconciliation of basic weighted-average shares outstanding to diluted weighted-average shares outstanding is as follows: Three Months Ended March 31, (in millions) 2018 2017 Basic weighted-average shares outstanding 152.2 159.4 Effect of dilutive securities (1) 2.6 3.4 Diluted weighted-average shares outstanding (2) 154.8 162.8 (1) The dilutive effect of outstanding stock options, restricted stock units, restricted stock, performance share units and Coworker Stock Purchase Plan units is reflected in the diluted weighted-average shares outstanding using the treasury stock method. (2) There were less than 1 million potential common shares excluded from diluted weighted-average shares outstanding for both the three months ended March 31, 2018 and 2017 as their inclusion would have had an anti-dilutive effect.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company is party to various legal proceedings that arise in the ordinary course of its business, which include commercial, intellectual property, employment, tort and other litigation matters. The Company is also subject to audit by federal, state, international, national, provincial and local authorities, and by various partners, group purchasing organizations and customers, including government agencies, relating to purchases and sales under various contracts. In addition, the Company is subject to indemnification claims under various contracts. From time to time, certain customers of the Company file voluntary petitions for reorganization or liquidation under the US bankruptcy laws or similar laws of the jurisdictions for the Company's business activities outside of the US. In such cases, certain pre-petition payments received by the Company could be considered preference items and subject to return to the bankruptcy administrator. As of March 31, 2018 , the Company does not believe that there is a reasonable possibility that any material loss exceeding the amounts already recognized for these proceedings and matters, if any, has been incurred. However, the ultimate resolutions of these proceedings and matters are inherently unpredictable. As such, the Company's financial condition and results of operations could be adversely affected in any particular period by the unfavorable resolution of one or more of these proceedings or matters.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment Information	Segment Information The Company has three reportable segments: Corporate, which is comprised primarily of US private sector business customers with more than 250 employees, Small Business, primarily servicing US private sector business customers with up to 250 employees, and Public, which is comprised of government agencies and education and healthcare institutions in the US. The Company has two other operating segments: CDW UK and CDW Canada, both of which do not meet the reportable segment quantitative thresholds and, accordingly, are included in an all other category ("Other"). Information about the Company's segments is as follows: (in millions) Corporate Small Business Public Other Headquarters Total Three Months Ended March 31, 2018 Net sales $ 1,565.8 $ 327.6 $ 1,230.0 $ 483.0 $ — $ 3,606.4 Income (loss) from operations 124.8 22.3 71.7 19.8 (34.5 ) 204.1 Depreciation and amortization expense (21.1 ) (5.2 ) (11.2 ) (8.8 ) (20.3 ) (66.6 ) Three Months Ended March 31, 2017 (1) Net sales $ 1,440.6 $ 292.0 $ 1,153.7 $ 369.7 $ — $ 3,256.0 Income (loss) from operations 112.1 16.6 60.8 12.7 (31.5 ) 170.7 Depreciation and amortization expense (20.8 ) (5.1 ) (11.2 ) (7.2 ) (19.9 ) (64.2 ) (1) Amounts for 2017 have been adjusted to reflect the adoption of Topic 606. Geographic Areas and Revenue Mix Three Months Ended March 31, 2018 Corporate Small Business Public Other Total Geography (1) United States $ 1,564.4 $ 327.6 $ 1,230.0 $ 9.2 $ 3,131.2 Rest of World 1.4 — — 473.8 475.2 Total Net sales 1,565.8 327.6 1,230.0 483.0 3,606.4 Major Product and Services Hardware 1,251.6 272.8 1,008.2 379.5 2,912.1 Software 219.6 43.1 183.1 59.3 505.1 Services 78.1 6.3 34.6 42.2 161.2 Other (2) 16.5 5.4 4.1 2.0 28.0 Total Net sales 1,565.8 327.6 1,230.0 483.0 3,606.4 Sales by Channel Corporate 1,565.8 — — — 1,565.8 Small Business — 327.6 — — 327.6 Government — — 418.5 — 418.5 Education — — 397.2 — 397.2 Healthcare — — 414.3 — 414.3 Other — — — 483.0 483.0 Total Net sales 1,565.8 327.6 1,230.0 483.0 3,606.4 Timing of Revenue Recognition Transferred at a point in time where CDW is principal 1,426.3 309.4 1,171.4 433.0 3,340.1 Transferred at a point in time where CDW is agent 92.7 16.5 41.1 15.1 165.4 Transferred over time where CDW is principal 46.8 1.7 17.5 34.9 100.9 Total Net sales $ 1,565.8 $ 327.6 $ 1,230.0 $ 483.0 $ 3,606.4 (1) Net sales by Geography is generally based on the ship-to address with the exception of certain services that may be performed at, or on behalf of, multiple locations. Such service arrangements are categorized based on the bill-to address. (2) Includes items such as delivery charges to customers. Three Months Ended March 31, 2017 (1) Corporate Small Business Public Other Total Geography (2) United States $ 1,439.5 $ 292.0 $ 1,153.7 $ 6.1 $ 2,891.3 Rest of World 1.1 — — 363.6 364.7 Total Net sales 1,440.6 292.0 1,153.7 369.7 3,256.0 Major Product and Services Hardware 1,146.5 240.8 958.6 293.5 2,639.4 Software 202.0 39.9 162.8 43.2 447.9 Services 75.8 6.2 28.0 31.3 141.3 Other (3) 16.3 5.1 4.3 1.7 27.4 Total Net sales 1,440.6 292.0 1,153.7 369.7 3,256.0 Sales by Channel Corporate 1,440.6 — — — 1,440.6 Small Business — 292.0 — — 292.0 Government — — 374.6 — 374.6 Education — — 393.2 — 393.2 Healthcare — — 385.9 — 385.9 Other — — — 369.7 369.7 Total Net sales 1,440.6 292.0 1,153.7 369.7 3,256.0 Timing of Revenue Recognition Transferred at a point in time where CDW is principal 1,314.2 275.7 1,105.8 331.5 3,027.2 Transferred at a point in time where CDW is agent 81.3 14.0 37.5 8.2 141.0 Transferred over time where CDW is principal 45.1 2.3 10.4 30.0 87.8 Total Net sales $ 1,440.6 $ 292.0 $ 1,153.7 $ 369.7 $ 3,256.0 (1) Amounts for 2017 have been adjusted to reflect the adoption of Topic 606. (2) Net sales by Geography is generally based on the ship-to address with the exception of certain services that may be performed at, or on behalf of, multiple locations. Such service arrangements are categorized based on the bill-to address. (3) Includes items such as delivery charges to customers. The following table presents Net sales by major category for the three months ended March 31, 2018 and 2017 . Categories are based upon internal classifications. Three Months Ended March 31, 2018 2017 (1) Dollars in Percentage Dollars in Percentage Notebooks/Mobile Devices $ 858.7 23.8 % $ 735.5 22.6 % Netcomm Products 482.9 13.4 458.6 14.1 Desktops 303.5 8.4 263.2 8.1 Video 259.2 7.2 235.7 7.2 Enterprise and Data Storage (Including Drives) 256.0 7.1 234.8 7.2 Other Hardware 751.8 20.8 711.6 21.9 Total Hardware 2,912.1 80.7 2,639.4 81.1 Software (2) 505.1 14.0 447.9 13.8 Services (2) 161.2 4.5 141.3 4.3 Other (3) 28.0 0.8 27.4 0.8 Total Net sales $ 3,606.4 100.0 % $ 3,256.0 100.0 % (1) Amounts for 2017 have been adjusted to reflect the adoption of Topic 606. (2) Certain software and services revenues are recorded on a net basis for accounting purposes. As a result, the category percentage of net revenues is not representative of the category percentage of gross profits. (3) Includes items such as delivery charges to customers.

Supplemental Guarantor Informat

Supplemental Guarantor Information	3 Months Ended
	Mar. 31, 2018
Supplemental Guarantor Information [Abstract]
Supplemental Guarantor Information	Supplemental Guarantor Information The 2023 Senior Notes, the 2024 Senior Notes and the 2025 Senior Notes are guaranteed by the Parent and each of CDW LLC’s direct and indirect, 100% owned, domestic subsidiaries (the "Guarantor Subsidiaries"). All guarantees by the Parent and the Guarantor Subsidiaries are and were joint and several, and full and unconditional; provided that guarantees by the Guarantor Subsidiaries are subject to certain customary release provisions contained in the indentures governing the 2023 Senior Notes, the 2024 Senior Notes and the 2025 Senior Notes. CDW LLC's 100% owned foreign subsidiaries, CDW International Holdings Limited, which is comprised of CDW UK and CDW Canada (together the "Non-Guarantor Subsidiaries"), do not guarantee the debt obligations. CDW LLC and CDW Finance Corporation, as co-issuers, are 100% owned by Parent and each of the Guarantor Subsidiaries and the Non-Guarantor Subsidiaries are, directly or indirectly, 100% owned by CDW LLC. The following tables set forth Condensed Consolidating Balance Sheets as of March 31, 2018 and December 31, 2017 , Consolidating Statements of Operations for the three months ended March 31, 2018 and 2017 , Condensed Consolidating Statements of Comprehensive Income for the three months ended March 31, 2018 and 2017 and Condensed Consolidating Statements of Cash Flows for the three months ended March 31, 2018 and 2017 , in accordance with Rule 3-10 of Regulation S-X. The consolidating financial information includes the accounts of CDW Corporation (the "Parent Guarantor"), which has no independent assets or operations, the accounts of CDW LLC (the "Subsidiary Issuer"), the combined accounts of the Guarantor Subsidiaries, the accounts of the Non-Guarantor Subsidiaries, and the accounts of CDW Finance Corporation (the "Co-Issuer") for the periods indicated. The information was prepared on the same basis as the Consolidated Financial Statements. Condensed Consolidating Balance Sheet March 31, 2018 (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Assets Current assets: Cash and cash equivalents $ — $ 173.3 $ — $ 65.9 $ — $ (18.2 ) $ 221.0 Accounts receivable, net — — 1,898.8 375.2 — — 2,274.0 Merchandise inventory — — 401.0 84.8 — — 485.8 Miscellaneous receivables — 105.2 182.7 22.3 — — 310.2 Prepaid expenses and other — 21.5 119.9 47.5 — — 188.9 Total current assets — 300.0 2,602.4 595.7 — (18.2 ) 3,479.9 Property and equipment, net — 87.7 42.1 23.3 — — 153.1 Goodwill — 751.8 1,439.0 298.0 — — 2,488.8 Other intangible assets, net — 277.4 388.6 193.0 — — 859.0 Other assets 1.6 52.1 207.5 2.8 — (216.9 ) 47.1 Investment in and advances to subsidiaries 995.3 3,016.8 — — — (4,012.1 ) — Total Assets $ 996.9 $ 4,485.8 $ 4,679.6 $ 1,112.8 $ — $ (4,247.2 ) $ 7,027.9 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable-trade $ — $ 24.6 $ 1,063.6 $ 218.5 $ — $ (18.2 ) $ 1,288.5 Accounts payable-inventory financing — — 481.8 41.9 — — 523.7 Current maturities of long-term debt — 14.9 3.8 7.1 — — 25.8 Contract liabilities — — 100.4 93.2 — — 193.6 Accrued expenses and other current liabilities — 210.6 263.4 76.9 — — 550.9 Total current liabilities — 250.1 1,913.0 437.6 — (18.2 ) 2,582.5 Long-term liabilities: Debt — 3,131.2 8.3 70.2 — — 3,209.7 Deferred income taxes — 69.0 89.3 32.2 — (1.6 ) 188.9 Other liabilities — 40.2 4.9 220.1 — (215.3 ) 49.9 Total long-term liabilities — 3,240.4 102.5 322.5 — (216.9 ) 3,448.5 Total stockholders' equity 996.9 995.3 2,664.1 352.7 — (4,012.1 ) 996.9 Total Liabilities and Stockholders' Equity $ 996.9 $ 4,485.8 $ 4,679.6 $ 1,112.8 $ — $ (4,247.2 ) $ 7,027.9 Condensed Consolidating Balance Sheet December 31, 2017 (as adjusted) (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Assets Current assets: Cash and cash equivalents $ — $ 113.7 $ — $ 32.4 $ — $ (1.9 ) $ 144.2 Accounts receivable, net — — 2,015.7 313.6 — — 2,329.3 Merchandise inventory — — 354.6 56.9 — — 411.5 Miscellaneous receivables — 103.9 211.1 28.0 — — 343.0 Prepaid expenses and other — 18.0 100.4 49.9 — — 168.3 Total current assets — 235.6 2,681.8 480.8 — (1.9 ) 3,396.3 Property and equipment, net — 95.0 43.5 22.6 — — 161.1 Goodwill — 751.8 1,439.0 288.8 — — 2,479.6 Other intangible assets, net — 280.1 424.5 192.4 — — 897.0 Other assets 1.7 30.7 209.3 2.6 — (211.6 ) 32.7 Investment in and advances to subsidiaries 983.9 3,066.1 — — — (4,050.0 ) — Total Assets $ 985.6 $ 4,459.3 $ 4,798.1 $ 987.2 $ — $ (4,263.5 ) $ 6,966.7 Liabilities and Stockholders' Equity Current liabilities: Accounts payable-trade $ — $ 42.5 $ 1,112.1 $ 165.0 $ — $ (1.9 ) $ 1,317.7 Accounts payable-inventory financing — 1.0 480.9 16.1 — — 498.0 Current maturities of long-term debt — 14.9 3.8 6.8 — — 25.5 Contract liabilities — — 87.5 71.3 — — 158.8 Accrued expenses and other current liabilities — 173.3 262.0 86.8 — — 522.1 Total current liabilities — 231.7 1,946.3 346.0 — (1.9 ) 2,522.1 Long-term liabilities: Debt — 3,134.2 8.3 67.5 — — 3,210.0 Deferred income taxes — 66.5 100.1 31.4 — (1.7 ) 196.3 Other liabilities — 43.0 4.7 214.9 — (209.9 ) 52.7 Total long-term liabilities — 3,243.7 113.1 313.8 — (211.6 ) 3,459.0 Total stockholders' equity 985.6 983.9 2,738.7 327.4 — (4,050.0 ) 985.6 Total Liabilities and Stockholders' Equity $ 985.6 $ 4,459.3 $ 4,798.1 $ 987.2 $ — $ (4,263.5 ) $ 6,966.7 Consolidating Statement of Operations Three Months Ended March 31, 2018 (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Net sales $ — $ — $ 3,123.4 $ 483.0 $ — $ — $ 3,606.4 Cost of sales — — 2,597.0 405.5 — — 3,002.5 Gross profit — — 526.4 77.5 — — 603.9 Selling and administrative expenses — 34.5 272.4 55.8 — — 362.7 Advertising expense — — 35.2 1.9 — — 37.1 Income (loss) from operations — (34.5 ) 218.8 19.8 — — 204.1 Interest (expense) income, net — (37.1 ) 1.0 (1.6 ) — — (37.7 ) Other (expense) income — — 0.4 (1.1 ) — — (0.7 ) Income (loss) before income taxes — (71.6 ) 220.2 17.1 — — 165.7 Income tax (expense) benefit (0.1 ) 20.8 (55.3 ) (4.1 ) — — (38.7 ) Income (loss) before equity in earnings of subsidiaries (0.1 ) (50.8 ) 164.9 13.0 — — 127.0 Equity in earnings of subsidiaries 127.1 177.9 — — — (305.0 ) — Net income $ 127.0 $ 127.1 $ 164.9 $ 13.0 $ — $ (305.0 ) $ 127.0 Consolidating Statement of Operations Three Months Ended March 31, 2017 (as adjusted) (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Net sales $ — $ — $ 2,886.3 $ 369.7 $ — $ — $ 3,256.0 Cost of sales — — 2,393.0 309.5 — — 2,702.5 Gross profit — — 493.3 60.2 — — 553.5 Selling and administrative expenses — 31.5 269.8 46.1 — — 347.4 Advertising expense — — 34.0 1.4 — — 35.4 Income (loss) from operations — (31.5 ) 189.5 12.7 — — 170.7 Interest (expense) income, net — (39.1 ) 1.0 (1.6 ) — — (39.7 ) Net loss on extinguishments of long-term debt — (57.4 ) — — — — (57.4 ) Other income — — 0.2 0.7 — — 0.9 Income (loss) before income taxes — (128.0 ) 190.7 11.8 — — 74.5 Income tax (expense) benefit — 57.3 (70.6 ) (3.0 ) — — (16.3 ) Income (loss) before equity in earnings of subsidiaries — (70.7 ) 120.1 8.8 — — 58.2 Equity in earnings of subsidiaries 58.2 128.9 — — — (187.1 ) — Net income $ 58.2 $ 58.2 $ 120.1 $ 8.8 $ — $ (187.1 ) $ 58.2 Condensed Consolidating Statement of Comprehensive Income Three Months Ended March 31, 2018 (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Comprehensive income $ 144.4 $ 144.5 $ 164.9 $ 27.2 $ — $ (336.6 ) $ 144.4 Condensed Consolidating Statement of Comprehensive Income Three Months Ended March 31, 2017 (as adjusted) (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Comprehensive income $ 64.3 $ 64.3 $ 120.1 $ 15.3 $ — $ (199.7 ) $ 64.3 Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2018 (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Net cash provided by (used in) operating activities $ — $ (13.8 ) $ 239.6 $ 10.8 $ — $ (14.4 ) $ 222.2 Cash flows used in investing activities: Capital expenditures — (11.1 ) (1.2 ) (3.6 ) — — (15.9 ) Net cash used in investing activities — (11.1 ) (1.2 ) (3.6 ) — — (15.9 ) Cash flows (used in) provided by financing activities: Proceeds from borrowings under revolving credit facilities — 163.0 — 7.0 — — 170.0 Repayments of borrowings under revolving credit facilities — (163.0 ) — (7.0 ) — — (170.0 ) Repayments of long-term debt — (3.7 ) — — — — (3.7 ) Net change in accounts payable-inventory financing — (0.9 ) 1.0 24.8 — — 24.9 Premium payments on interest rate cap agreements — (12.6 ) — — — — (12.6 ) Proceeds from stock option exercises — 7.3 — — — — 7.3 Proceeds from Coworker Stock Purchase Plan — 2.4 — — — — 2.4 Repurchases of common stock (109.2 ) — — — — — (109.2 ) Payment of incentive compensation plan withholding taxes (8.7 ) — — — — — (8.7 ) Dividends (32.0 ) — — — — — (32.0 ) Other — 0.7 (0.1 ) (0.2 ) — — 0.4 Distributions and advances from (to) affiliates 149.9 91.3 (239.3 ) — — (1.9 ) — Net cash (used in) provided by financing activities — 84.5 (238.4 ) 24.6 — (1.9 ) (131.2 ) Effect of exchange rate changes on cash and cash equivalents — — — 1.7 — — 1.7 Net increase in cash and cash equivalents — 59.6 — 33.5 — (16.3 ) 76.8 Cash and cash equivalents—beginning of period — 113.7 — 32.4 — (1.9 ) 144.2 Cash and cash equivalents—end of period $ — $ 173.3 $ — $ 65.9 $ — $ (18.2 ) $ 221.0 Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2017 (as adjusted) (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Net cash provided by operating activities $ — $ 24.5 $ 333.2 $ 38.2 $ — $ (26.0 ) $ 369.9 Cash flows from investing activities: Capital expenditures — (14.6 ) (2.4 ) (2.6 ) — — (19.6 ) Net cash used in investing activities — (14.6 ) (2.4 ) (2.6 ) — — (19.6 ) Cash flows (used in) provided by financing activities: Proceeds from borrowings under revolving credit facilities — 38.0 — 6.1 — — 44.1 Repayments of borrowings under revolving credit facilities — — — (6.1 ) — — (6.1 ) Repayments of long-term debt — (3.7 ) — — — — (3.7 ) Proceeds from issuance of long-term debt — 2,083.0 — — — — 2,083.0 Payments to extinguish long-term debt — (2,121.3 ) — — — — (2,121.3 ) Payment of debt financing fees — (9.6 ) — — — — (9.6 ) Net change in accounts payable-inventory financing — (0.9 ) (132.2 ) (2.6 ) — — (135.7 ) Proceeds from stock option exercises — 4.4 — — — — 4.4 Proceeds from Coworker Stock Purchase Plan — 2.1 — — — — 2.1 Repurchases of common stock (175.4 ) — — — — — (175.4 ) Payment of incentive compensation plan withholding taxes — (10.4 ) (7.7 ) (0.2 ) — — (18.3 ) Dividends (25.5 ) — — — — — (25.5 ) Other — — — (0.2 ) — — (0.2 ) Distributions and advances from (to) affiliates 200.9 (9.3 ) (194.0 ) — — 2.4 — Net cash used in financing activities — (27.7 ) (333.9 ) (3.0 ) — 2.4 (362.2 ) Effect of exchange rate changes on cash and cash equivalents — — — (0.1 ) — — (0.1 ) Net (decrease) increase in cash and cash equivalents — (17.8 ) (3.1 ) 32.5 — (23.6 ) (12.0 ) Cash and cash equivalents—beginning of period — 222.7 3.1 37.9 — — 263.7 Cash and cash equivalents—end of period $ — $ 204.9 $ — $ 70.4 $ — $ (23.6 ) $ 251.7

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On April 3, 2018 , the Company amended the Term Loan to reprice the Revolving Loan, reducing interest margins by 25 basis points. Borrowings under the Term Loan continue to bear interest at either (i) the ABR plus a margin or (ii) LIBOR plus a margin based upon a net leverage ratio as defined in the agreement governing the Term Loan. The amended margin is 0.75% for ABR borrowings and 1.75% for LIBOR borrowings effective April 3, 2018 . Additionally, the Company amended its covenant on restricted payments, such that the Company is permitted to make restricted payments so long as the total net leverage ratio is less than 3.75 :1.00.

Description of Business and S21

Description of Business and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Description of Business	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 ("US"), the United Kingdom ("UK") and Canada. 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 as described in Note 12 (Supplemental Guarantor Information) and does not hold any material assets or engage in any business activities or operations.
Basis of Presentation	Basis of Presentation The accompanying unaudited interim Consolidated Financial Statements as of March 31, 2018 and for the three months ended March 31, 2018 and 2017 (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 and the notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 (the " December 31, 2017 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, 2017 Consolidated Financial Statements except for changes from the adoption of Accounting Standards Update ("ASU") 2014-09, Revenue from Contracts with Customers, as amended ("Topic 606"), as discussed below. 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. Effective January 1, 2018, the Company adopted the requirements of Topic 606 utilizing the full retrospective method as discussed in Note 2 (Recent Accounting Pronouncements) . Prior period amounts have been adjusted accordingly.
Principles of Consolidation	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	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, 2017 Consolidated Financial Statements include a discussion of the significant accounting policies and estimates used in the preparation of the Company's Consolidated Financial Statements. Except as noted above for the adoption of Topic 606, there have been no material changes to the Company's significant accounting policies and estimates during the three months ended March 31, 2018 .
Revenue Recognition	Revenue Recognition The Company is a primary distribution channel for a large group of vendors and suppliers, including original equipment manufacturers ("OEMs"), software publishers and wholesale distributors. The Company accounts for a contract when it has approval and commitment from both parties, the rights of the parties are identified, payment terms are established, the contract has commercial substance and collectability of consideration is probable. The Company considers the following indicators amongst others when determining whether it is acting as a principal in the transaction and recording revenue on a gross basis: (i) the Company is primarily responsible for fulfilling the promise to provide the specified goods or service, (ii) the Company has inventory risk before the specified good or service has been transferred to a customer or after transfer of control to the customer and (iii) the Company has discretion in establishing the price for the specified good or service. If a transaction does not meet the Company's indicators of being a principal in the transaction, then the Company is acting as an agent in the transaction and the associated revenues are recognized on a net basis. The Company recognizes revenue once control has passed to the customer. The following indicators are evaluated in determining when control has passed to the customer: (i) the Company has a right to payment for the product or service, (ii) the customer has legal title to the product, (iii) the Company has transferred physical possession of the product to the customer, (iv) the customer has the significant risk and rewards of ownership of the product and (v) the customer has accepted the product. The Company's products can be delivered to customers in a variety of ways, including (i) as physical product shipped from the Company's warehouse, (ii) via drop-shipment by the vendor or supplier or (iii) via electronic delivery of keys for software licenses. The Company’s shipping terms typically specify F.O.B. destination. The Company leverages drop-shipment arrangements with many of its vendors and suppliers to deliver products to its customers without having to physically hold the inventory at its warehouses. The Company is the principal in the transaction and recognizes revenue for drop-shipment arrangements on a gross basis. Revenue Recognition for Hardware Revenues from sales of hardware products are recognized on a gross basis as the Company is acting as a principal in these transactions, with the selling price to the customer recorded as Net sales and the acquisition cost of the product recorded as Cost of sales. The Company recognizes revenue from these transactions when control has passed to the customer, which is usually upon delivery of the product to the customer. In some instances, the customer agrees to buy the product from the Company but requests delivery at a later date, commonly known as bill-and-hold arrangements. For these transactions, the Company deems that control passes to the customer when the product is ready for delivery. The Company views products ready for delivery when the customer has a signed agreement, significant risk and rewards for the products, the ability to direct the assets, the products have been set aside specifically for the customer, cannot be redirected to another customer and for customer orders that include configuration services, when such services have been completed. Revenue Recognition for Software Revenues from most software license sales are recognized as a single performance obligation on a gross basis as the Company is acting as a principal in these transactions at the point the software license is delivered to the customer. Generally, software licenses are sold with accompanying third-party delivered software assurance, which is a product that allows customers to upgrade, at no additional cost, to the latest technology if new capabilities are introduced during the period that the software assurance is in effect. The Company evaluates whether the software assurance is a separate performance obligation by assessing if the third-party delivered software assurance is critical or essential to the core functionality of the software itself. This involves considering if the software provides its original intended functionality to the customer without the updates, if the customer would ascribe a higher value to the upgrades versus the up-front deliverable, if the customer would expect frequent intelligence updates to the software (such as updates that maintain the original functionality), and if the customer chooses to not delay or always install upgrades. If the Company determines that the accompanying third-party delivered software assurance is critical or essential to the core functionality of the software license, the software license and the accompanying third-party delivered software assurance are recognized as a single performance obligation. The value of the product is primarily the accompanying support delivered by a third-party and therefore the Company is acting as an agent in these transactions and recognizes them on a net basis at the point the associated software license is delivered to the customer. For software licenses where the accompanying third-party delivered software assurance is not critical or essential to the core functionality, the software assurance is recognized as a separate performance obligation, with the associated revenue recognized on a net basis at the point the related software license is delivered to the customer. For additional details regarding the accounting for bundled arrangements, see "Revenue Recognition for Bundled Arrangements" below. The Company's vendor partners warrant most of the products the Company sells. These manufacturer warranties are assurance-type warranties and are not considered separate performance obligations. The warranties are not sold separately and only provide assurance that products will conform with the manufacturer's specifications. In some transactions, a third-party will provide the customer with an extended warranty. These extended warranties are sold separately and provide the customer with a service in addition to assurance that the product will function as expected. The Company considers these service-type warranties to be separate performance obligations from the underlying product. For service-type warranties, the Company is arranging for those services to be provided by the third-party and therefore is acting as an agent in the transaction and records revenue on a net basis at the point of sale. Revenue Recognition for Services The Company provides professional services, which include project managers and consultants recommending, designing and implementing IT solutions. Revenue from professional services is recognized either on a time and materials basis or recognized proportionally as costs are incurred for fixed fee project work. For time and materials projects, revenue is recognized on a gross basis each month as work is performed and the Company transfers those services. The Company sells cloud computing solutions, which include Software as a Service ("SaaS") and Infrastructure as a Service ("IaaS"). SaaS solutions utilize third-party partners to offer the Company's customers access to software in the cloud that enhances office productivity, provides security or assists in collaboration. IaaS solutions utilize third-party partners to enable customers to access data center functionality in a cloud-based solution, including storage, computing and networking. The Company recognizes revenue for cloud computing solutions for arrangements with one-time invoicing to the customer at the time of invoice on a net basis as the Company is acting as an agent in the transaction. For subscription-based arrangements with monthly billing, the Company is acting as an agent in the transaction and recognizes revenue as it invoices the customer for its monthly usage on a net basis. Revenues from the sale of data center services, such as managed and remote managed services, server co-location, internet connectivity and data backup and storage provided by the Company, are recognized over the period the service is provided. Most hosting and managed service obligations are based on the quantity and pricing parameters established in the agreement. As the customer receives the benefit of service each month, the Company recognizes the respective revenue on a gross basis as the Company is acting as a principal in the transaction. Additionally, the Company's managed services team provides project support to customers that are billed on a fixed fee basis. The Company is acting as the principal in the transaction and recognizes revenue on a gross basis based on the total number of hours incurred for the period over the total expected hours for the project. Total expected hours to complete the project is updated for each period and best represents the transfer of control of the service to the customer. The Company's customers are offered the opportunity by certain of its vendors to purchase software licenses and software assurance under enterprise agreements ("EAs"), referred to as services in this paragraph. For most EA transactions, the Company's obligation to the customer is that of a distributor or sales agent of the services, where all obligations for providing the services to customers are passed to the Company's vendors. The Company's performance obligations are satisfied at the time of the sale. In other EA transactions, the Company is responsible for fulfilling the promised services to the customer and providing remedy or refund for work if the customer is not satisfied with the delivered services, has inventory risk in the arrangement and has full control to set the price for the customer. This results in the Company acting as a principal in the agreement. With most EAs, the Company's vendors will transfer the license and invoice the customer directly, paying resellers an agency fee or commission on these sales. The Company records these fees as a component of Net sales as earned and there is no corresponding Cost of sales amount. Revenue Recognition for Bundled Arrangements The Company also sells some of its products and services as part of bundled contract arrangements containing multiple deliverables, which may include a combination of products and services. For each deliverable that represents a distinct performance obligation, total arrangement consideration is allocated based upon the standalone selling prices of each performance obligation. The Company excludes amounts collected on behalf of third-parties, such as sales taxes, when determining the transaction price. For certain performance obligations, the Company will use a combination of methods to estimate the standalone selling price. When evidence from recent transactions is not available to confirm that the prices are representative of the standalone selling price, an expected cost plus a margin approach is used. Sales In-Transit The Company performs an analysis of the estimated number of days of sales in-transit to customers at the end of each reporting period based on a weighted-average analysis of commercial delivery terms that include drop-shipment arrangements. This analysis is the basis upon which the Company estimates the amount of Net sales in-transit at the end of the period and adjusts revenue and the related costs to reflect only what has been delivered to the customer. Changes in delivery patterns may result in a different number of business days estimated to make this adjustment. Freight Costs The Company records freight billed to its customers as Net sales and the related freight costs as a Cost of sales when product is shipped to the customer. For freight not billed to its customers, the Company records the freight costs as a Cost of sales. The Company's typical shipping terms are F.O.B destination, which results in shipping being performed before the customer obtains control of the product. The Company considers shipping to be a fulfillment activity and not a separate performance obligation. Other The nature of the Company's contracts give rise to variable consideration in the form of sales returns and allowances. The Company estimates variable consideration at the most likely amount to which it is expected to be entitled. This estimated amount is included in the transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. The estimates of variable consideration and determination of whether to include estimated amounts in the transaction price are based on an assessment of the Company's anticipated performance and all information that is reasonably available. At the time of sale, the Company records an estimate for sales returns and allowances and an associated right of return asset based on historical experience. When a contract results in revenue being recognized in excess of the amount the Company has the right to invoice to the customer, a contract asset is recorded on the balance sheet. Contract assets are comprised primarily of professional services with fixed fee arrangements. Contract liabilities consist of payments received from customers, or such consideration that is contractually due, in advance of providing the product or performing services. Contract liabilities are comprised primarily of professional services with fixed fee arrangements, bill-and-hold transactions where control has not passed to the customer and certain governmental contracts. Trade accounts receivable are recorded at the point of sale (or in accordance with the Statement of Work for services) for the total amount payable by the customer to the Company for sale of goods. Taxes to be collected from the customer as part of the sale are included in Accounts receivable trade. Any incremental direct costs of obtaining a contract are deferred on the Consolidated Balance Sheets and amortized over the period of contract performance. The Company typically does not enter into long-term contracts. The Company has elected to use the practical expedient for its performance obligations table to show only those contracts that are longer than 12 months at the time of contract inception and those contracts that are non-cancelable. Additionally, for certain governmental contracts where there are annual renewals, the Company has excluded these contracts since there is only a one-year legal obligation. Typically, the only contracts that are longer than 12 months in duration are related to the Company's professional and managed services business. The Company requests payments for its products and services at the point of sale. The Company generally does not enter into any long-term financing arrangements or payment plans with customers or contracts with customers that have non-cash consideration.
Recent Accounting Pronouncements	Accounting for Hedging Activities In August 2017, the Financial Accounting Standards Board (the "FASB") issued ASU 2017-12, Derivatives and Hedging (Topic 815), intending to improve the transparency of information included in the financial statements by aligning cash flow and fair value hedge accounting with its risk management activities. The ASU eliminates the requirement to separately measure and report hedge ineffectiveness for cash flow hedges and net investment hedges, and generally requires the entire change in the fair value of a hedging instrument to be presented in the same income statement line as the hedged item. The ASU also simplifies certain documentation and assessment requirements, and will incorporate new disclosure requirements and amendments to existing disclosures. This ASU is effective for the Company beginning the first quarter of 2019 and allows for early adoption. The Company is currently evaluating the impact the ASU will have on its Consolidated Financial Statements. Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This ASU introduces a new forward-looking approach, based on expected losses, to estimate credit losses on certain types of financial instruments, including trade receivables. The estimate of expected credit losses will require considerations of historical information, current information and reasonable and supportable forecasts. This ASU also expands the disclosure requirements to enable users of financial statements to understand the assumptions, models and methods for estimating expected credit losses. This ASU is effective for the Company beginning in the first quarter of 2020 and allows for early adoption beginning in the first quarter of 2019. The Company is currently evaluating the impact the ASU will have on its Consolidated Financial Statements. Accounting for Leases In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), requiring lessees to recognize assets and liabilities on the balance sheet for the rights and obligations created by long-term leases and to disclose additional quantitative and qualitative information about leasing arrangements. This ASU is effective for the Company beginning in the first quarter of 2019 and allows for early adoption. Although the Company is currently evaluating the provisions of the ASU to determine how it will be affected, the primary impact to the Company of the new ASU will be to record assets and liabilities for current operating leases, which are principally related to the Company's real estate portfolio. Revenue Recognition On January 1, 2018, the Company adopted Topic 606 and utilized the full retrospective method.

Recent Accounting Pronounceme22

Recent Accounting Pronouncements (Tables)	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	For the three months ended March 31, 2017 , the adoption of Topic 606 impacted the Company's results as follows: March 31, 2017 (in millions) (except per share amounts) As Reported New Revenue Standard Adjustment As Adjusted Net sales $ 3,324.7 $ (68.7 ) $ 3,256.0 Gross profit 552.6 0.9 553.5 Gross profit margin 16.6 % 40 bps 17.0 % Income from operations 169.8 0.9 170.7 Income tax expense (16.0 ) (0.3 ) (16.3 ) Net income $ 57.6 $ 0.6 $ 58.2 Net income per common share Basic $ 0.36 $ — $ 0.36 Diluted $ 0.35 $ 0.01 $ 0.36 The adoption of Topic 606 impacted the Company's Consolidated Balance Sheet as of December 31, 2017 as follows: December 31, 2017 (in millions) As Reported New Revenue Standard Adjustment As Adjusted (1) Accounts receivable $ 2,320.5 $ 8.8 $ 2,329.3 Merchandise inventory 449.5 (38.0 ) 411.5 Miscellaneous receivables 336.5 6.5 343.0 Prepaid expenses and other 127.4 40.9 168.3 Total current assets 3,378.1 18.2 3,396.3 Other assets 40.8 (8.1 ) 32.7 Total assets 6,956.6 10.1 6,966.7 Contract liabilities 194.0 (35.2 ) 158.8 Income tax payable 15.1 1.1 16.2 Other accrued expenses 180.2 41.6 221.8 Total current liabilities 2,514.6 7.5 2,522.1 Total liabilities 5,973.7 7.5 5,981.1 Total stockholders’ equity $ 982.9 $ 2.7 $ 985.6 (1) Amounts may not cross-foot due to rounding.

Inventory Financing Agreements

Inventory Financing Agreements (Tables)	3 Months Ended
	Mar. 31, 2018
Inventory Financing Agreements [Abstract]
Inventory Financing Agreements	Amounts included in Accounts payable-inventory financing are as follows: (in millions) March 31, 2018 December 31, 2017 Revolving Loan inventory financing agreement (1) $ 481.6 $ 480.9 Other inventory financing agreements 42.1 17.1 Accounts payable-inventory financing $ 523.7 $ 498.0 (1) The Senior Secured Asset-Based Revolving Credit Facility includes an inventory floorplan sub-facility that enables the Company to maintain an inventory financing agreement with a financial intermediary to facilitate the purchase of inventory from certain vendors on more favorable terms than offered directly by the vendors.

Contract Liabilities and Rema24

Contract Liabilities and Remaining Performance Obligations (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	The following table represents the total transaction price for the remaining performance obligations as of March 31, 2018 related to non-cancelable contracts longer than 12 months in duration that is expected to be recognized over future periods. (in millions) Within 1 Year Years 1-2 Years 2-3 Thereafter Remaining Performance Obligations $ 39.2 $ 25.6 $ 9.6 $ 0.7

Financial Instruments (Tables)

Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2018
Financial Instruments [Abstract]
Schedule of Interest Rate Derivatives	As of March 31, 2018 and December 31, 2017 , the Company had the following interest rate cap agreements for which the fair values are classified within Other assets on the Consolidated Balance Sheets: March 31, 2018 December 31, 2017 Notional Value (in millions) Effective Date Maturity Date Fair Value (in millions) Fair Value (in millions) $ 1,400.0 January 17, 2017 December 31, 2018 $ 8.8 $ 5.4 1,400.0 December 31, 2018 December 31, 2020 12.7 — $ 21.5 $ 5.4

Long-Term Debt (Tables)

Long-Term Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Long-term Debt, Unclassified [Abstract]
Schedule of Long-term Debt Instruments	Long-term debt as of March 31, 2018 is as follows: (dollars in millions) Interest Rate Principal Unamortized Discount and Deferred Financing Fees Total Senior secured asset-based revolving credit facility — % $ — $ — $ — CDW UK revolving credit facility — % — — — Senior secured term loan facility (1) 4.3 % 1,464.3 (2.0 ) 1,462.3 CDW UK term loan 2.0 % 78.5 (1.3 ) 77.2 Senior notes due 2023 5.0 % 525.0 (4.2 ) 520.8 Senior notes due 2024 5.5 % 575.0 (5.0 ) 570.0 Senior notes due 2025 5.0 % 600.0 (7.0 ) 593.0 Other long-term obligations 12.2 — 12.2 Total debt 3,255.0 (19.5 ) 3,235.5 Less current maturities (25.8 ) — (25.8 ) Long-term debt, excluding current maturities $ 3,229.2 $ (19.5 ) $ 3,209.7 (1) The Senior secured term loan facility has a variable interest rate, which has effectively been capped through the use of an interest rate cap (see Note 5 (Financial Instruments) ). The interest rate disclosed represents the variable interest rate in effect as of March 31, 2018 . Long-term debt as of December 31, 2017 is as follows: (dollars in millions) Interest Principal Unamortized Discount and Deferred Financing Fees Total Senior secured asset-based revolving credit facility — % $ — $ — $ — CDW UK revolving credit facility — % — — — Senior secured term loan facility (1) 3.7 % 1,468.0 (2.0 ) 1,466.0 CDW UK term loan 1.9 % 75.7 (1.4 ) 74.3 Senior notes due 2023 5.0 % 525.0 (4.5 ) 520.5 Senior notes due 2024 5.5 % 575.0 (5.2 ) 569.8 Senior notes due 2025 5.0 % 600.0 (7.3 ) 592.7 Other long-term obligations 12.2 — 12.2 Total debt 3,255.9 (20.4 ) 3,235.5 Less current maturities (25.5 ) — (25.5 ) Long-term debt, excluding current maturities $ 3,230.4 $ (20.4 ) $ 3,210.0 (1) The Senior secured term loan facility has a variable interest rate, which has effectively been capped through the use of an interest rate cap (see Note 5 (Financial Instruments) ). The interest rate disclosed represents the variable interest rate in effect as of December 31, 2017 .
Carrying Value of Long-Term Debt	Fair Value The fair values of the Senior Notes were estimated using quoted market prices for identical liabilities that are traded in over-the-counter secondary markets that are not considered active. The fair value of the Term Loan was estimated using dealer quotes for identical liabilities in markets that are not considered active. The Senior Notes, Term Loan and the CDW UK Term Loan are classified as Level 2 within the fair value hierarchy. The carrying value of the Revolving Loan and the CDW UK Revolving Credit Facility approximate fair value if there are outstanding borrowings. As of March 31, 2018 , the carrying value of the CDW UK Term Loan approximated fair value. The approximate fair values and related carrying values of the Company's long-term debt, including current maturities and excluding unamortized discount and unamortized deferred financing fees, were as follows: (in millions) March 31, 2018 December 31, 2017 Fair value $ 3,290.7 $ 3,366.5 Carrying value 3,255.0 3,255.9

Earnings per Share (Tables)

Earnings per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule of Weighted Average Number of Shares	A reconciliation of basic weighted-average shares outstanding to diluted weighted-average shares outstanding is as follows: Three Months Ended March 31, (in millions) 2018 2017 Basic weighted-average shares outstanding 152.2 159.4 Effect of dilutive securities (1) 2.6 3.4 Diluted weighted-average shares outstanding (2) 154.8 162.8 (1) The dilutive effect of outstanding stock options, restricted stock units, restricted stock, performance share units and Coworker Stock Purchase Plan units is reflected in the diluted weighted-average shares outstanding using the treasury stock method. (2) There were less than 1 million potential common shares excluded from diluted weighted-average shares outstanding for both the three months ended March 31, 2018 and 2017 as their inclusion would have had an anti-dilutive effect.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Information about the Company's segments is as follows: (in millions) Corporate Small Business Public Other Headquarters Total Three Months Ended March 31, 2018 Net sales $ 1,565.8 $ 327.6 $ 1,230.0 $ 483.0 $ — $ 3,606.4 Income (loss) from operations 124.8 22.3 71.7 19.8 (34.5 ) 204.1 Depreciation and amortization expense (21.1 ) (5.2 ) (11.2 ) (8.8 ) (20.3 ) (66.6 ) Three Months Ended March 31, 2017 (1) Net sales $ 1,440.6 $ 292.0 $ 1,153.7 $ 369.7 $ — $ 3,256.0 Income (loss) from operations 112.1 16.6 60.8 12.7 (31.5 ) 170.7 Depreciation and amortization expense (20.8 ) (5.1 ) (11.2 ) (7.2 ) (19.9 ) (64.2 ) (1) Amounts for 2017 have been adjusted to reflect the adoption of Topic 606.
Disaggregation of Revenue	Geographic Areas and Revenue Mix Three Months Ended March 31, 2018 Corporate Small Business Public Other Total Geography (1) United States $ 1,564.4 $ 327.6 $ 1,230.0 $ 9.2 $ 3,131.2 Rest of World 1.4 — — 473.8 475.2 Total Net sales 1,565.8 327.6 1,230.0 483.0 3,606.4 Major Product and Services Hardware 1,251.6 272.8 1,008.2 379.5 2,912.1 Software 219.6 43.1 183.1 59.3 505.1 Services 78.1 6.3 34.6 42.2 161.2 Other (2) 16.5 5.4 4.1 2.0 28.0 Total Net sales 1,565.8 327.6 1,230.0 483.0 3,606.4 Sales by Channel Corporate 1,565.8 — — — 1,565.8 Small Business — 327.6 — — 327.6 Government — — 418.5 — 418.5 Education — — 397.2 — 397.2 Healthcare — — 414.3 — 414.3 Other — — — 483.0 483.0 Total Net sales 1,565.8 327.6 1,230.0 483.0 3,606.4 Timing of Revenue Recognition Transferred at a point in time where CDW is principal 1,426.3 309.4 1,171.4 433.0 3,340.1 Transferred at a point in time where CDW is agent 92.7 16.5 41.1 15.1 165.4 Transferred over time where CDW is principal 46.8 1.7 17.5 34.9 100.9 Total Net sales $ 1,565.8 $ 327.6 $ 1,230.0 $ 483.0 $ 3,606.4 (1) Net sales by Geography is generally based on the ship-to address with the exception of certain services that may be performed at, or on behalf of, multiple locations. Such service arrangements are categorized based on the bill-to address. (2) Includes items such as delivery charges to customers. Three Months Ended March 31, 2017 (1) Corporate Small Business Public Other Total Geography (2) United States $ 1,439.5 $ 292.0 $ 1,153.7 $ 6.1 $ 2,891.3 Rest of World 1.1 — — 363.6 364.7 Total Net sales 1,440.6 292.0 1,153.7 369.7 3,256.0 Major Product and Services Hardware 1,146.5 240.8 958.6 293.5 2,639.4 Software 202.0 39.9 162.8 43.2 447.9 Services 75.8 6.2 28.0 31.3 141.3 Other (3) 16.3 5.1 4.3 1.7 27.4 Total Net sales 1,440.6 292.0 1,153.7 369.7 3,256.0 Sales by Channel Corporate 1,440.6 — — — 1,440.6 Small Business — 292.0 — — 292.0 Government — — 374.6 — 374.6 Education — — 393.2 — 393.2 Healthcare — — 385.9 — 385.9 Other — — — 369.7 369.7 Total Net sales 1,440.6 292.0 1,153.7 369.7 3,256.0 Timing of Revenue Recognition Transferred at a point in time where CDW is principal 1,314.2 275.7 1,105.8 331.5 3,027.2 Transferred at a point in time where CDW is agent 81.3 14.0 37.5 8.2 141.0 Transferred over time where CDW is principal 45.1 2.3 10.4 30.0 87.8 Total Net sales $ 1,440.6 $ 292.0 $ 1,153.7 $ 369.7 $ 3,256.0 (1) Amounts for 2017 have been adjusted to reflect the adoption of Topic 606. (2) Net sales by Geography is generally based on the ship-to address with the exception of certain services that may be performed at, or on behalf of, multiple locations. Such service arrangements are categorized based on the bill-to address. (3) Includes items such as delivery charges to customers. The following table presents Net sales by major category for the three months ended March 31, 2018 and 2017 . Categories are based upon internal classifications. Three Months Ended March 31, 2018 2017 (1) Dollars in Percentage Dollars in Percentage Notebooks/Mobile Devices $ 858.7 23.8 % $ 735.5 22.6 % Netcomm Products 482.9 13.4 458.6 14.1 Desktops 303.5 8.4 263.2 8.1 Video 259.2 7.2 235.7 7.2 Enterprise and Data Storage (Including Drives) 256.0 7.1 234.8 7.2 Other Hardware 751.8 20.8 711.6 21.9 Total Hardware 2,912.1 80.7 2,639.4 81.1 Software (2) 505.1 14.0 447.9 13.8 Services (2) 161.2 4.5 141.3 4.3 Other (3) 28.0 0.8 27.4 0.8 Total Net sales $ 3,606.4 100.0 % $ 3,256.0 100.0 % (1) Amounts for 2017 have been adjusted to reflect the adoption of Topic 606. (2) Certain software and services revenues are recorded on a net basis for accounting purposes. As a result, the category percentage of net revenues is not representative of the category percentage of gross profits. (3) Includes items such as delivery charges to customers.

Supplemental Guarantor Inform29

Supplemental Guarantor Information (Tables)	3 Months Ended
	Mar. 31, 2018
Supplemental Guarantor Information [Abstract]
Condensed Consolidating Balance Sheets	Condensed Consolidating Balance Sheet March 31, 2018 (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Assets Current assets: Cash and cash equivalents $ — $ 173.3 $ — $ 65.9 $ — $ (18.2 ) $ 221.0 Accounts receivable, net — — 1,898.8 375.2 — — 2,274.0 Merchandise inventory — — 401.0 84.8 — — 485.8 Miscellaneous receivables — 105.2 182.7 22.3 — — 310.2 Prepaid expenses and other — 21.5 119.9 47.5 — — 188.9 Total current assets — 300.0 2,602.4 595.7 — (18.2 ) 3,479.9 Property and equipment, net — 87.7 42.1 23.3 — — 153.1 Goodwill — 751.8 1,439.0 298.0 — — 2,488.8 Other intangible assets, net — 277.4 388.6 193.0 — — 859.0 Other assets 1.6 52.1 207.5 2.8 — (216.9 ) 47.1 Investment in and advances to subsidiaries 995.3 3,016.8 — — — (4,012.1 ) — Total Assets $ 996.9 $ 4,485.8 $ 4,679.6 $ 1,112.8 $ — $ (4,247.2 ) $ 7,027.9 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable-trade $ — $ 24.6 $ 1,063.6 $ 218.5 $ — $ (18.2 ) $ 1,288.5 Accounts payable-inventory financing — — 481.8 41.9 — — 523.7 Current maturities of long-term debt — 14.9 3.8 7.1 — — 25.8 Contract liabilities — — 100.4 93.2 — — 193.6 Accrued expenses and other current liabilities — 210.6 263.4 76.9 — — 550.9 Total current liabilities — 250.1 1,913.0 437.6 — (18.2 ) 2,582.5 Long-term liabilities: Debt — 3,131.2 8.3 70.2 — — 3,209.7 Deferred income taxes — 69.0 89.3 32.2 — (1.6 ) 188.9 Other liabilities — 40.2 4.9 220.1 — (215.3 ) 49.9 Total long-term liabilities — 3,240.4 102.5 322.5 — (216.9 ) 3,448.5 Total stockholders' equity 996.9 995.3 2,664.1 352.7 — (4,012.1 ) 996.9 Total Liabilities and Stockholders' Equity $ 996.9 $ 4,485.8 $ 4,679.6 $ 1,112.8 $ — $ (4,247.2 ) $ 7,027.9 Condensed Consolidating Balance Sheet December 31, 2017 (as adjusted) (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Assets Current assets: Cash and cash equivalents $ — $ 113.7 $ — $ 32.4 $ — $ (1.9 ) $ 144.2 Accounts receivable, net — — 2,015.7 313.6 — — 2,329.3 Merchandise inventory — — 354.6 56.9 — — 411.5 Miscellaneous receivables — 103.9 211.1 28.0 — — 343.0 Prepaid expenses and other — 18.0 100.4 49.9 — — 168.3 Total current assets — 235.6 2,681.8 480.8 — (1.9 ) 3,396.3 Property and equipment, net — 95.0 43.5 22.6 — — 161.1 Goodwill — 751.8 1,439.0 288.8 — — 2,479.6 Other intangible assets, net — 280.1 424.5 192.4 — — 897.0 Other assets 1.7 30.7 209.3 2.6 — (211.6 ) 32.7 Investment in and advances to subsidiaries 983.9 3,066.1 — — — (4,050.0 ) — Total Assets $ 985.6 $ 4,459.3 $ 4,798.1 $ 987.2 $ — $ (4,263.5 ) $ 6,966.7 Liabilities and Stockholders' Equity Current liabilities: Accounts payable-trade $ — $ 42.5 $ 1,112.1 $ 165.0 $ — $ (1.9 ) $ 1,317.7 Accounts payable-inventory financing — 1.0 480.9 16.1 — — 498.0 Current maturities of long-term debt — 14.9 3.8 6.8 — — 25.5 Contract liabilities — — 87.5 71.3 — — 158.8 Accrued expenses and other current liabilities — 173.3 262.0 86.8 — — 522.1 Total current liabilities — 231.7 1,946.3 346.0 — (1.9 ) 2,522.1 Long-term liabilities: Debt — 3,134.2 8.3 67.5 — — 3,210.0 Deferred income taxes — 66.5 100.1 31.4 — (1.7 ) 196.3 Other liabilities — 43.0 4.7 214.9 — (209.9 ) 52.7 Total long-term liabilities — 3,243.7 113.1 313.8 — (211.6 ) 3,459.0 Total stockholders' equity 985.6 983.9 2,738.7 327.4 — (4,050.0 ) 985.6 Total Liabilities and Stockholders' Equity $ 985.6 $ 4,459.3 $ 4,798.1 $ 987.2 $ — $ (4,263.5 ) $ 6,966.7
Consolidating Statements of Operations	Consolidating Statement of Operations Three Months Ended March 31, 2018 (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Net sales $ — $ — $ 3,123.4 $ 483.0 $ — $ — $ 3,606.4 Cost of sales — — 2,597.0 405.5 — — 3,002.5 Gross profit — — 526.4 77.5 — — 603.9 Selling and administrative expenses — 34.5 272.4 55.8 — — 362.7 Advertising expense — — 35.2 1.9 — — 37.1 Income (loss) from operations — (34.5 ) 218.8 19.8 — — 204.1 Interest (expense) income, net — (37.1 ) 1.0 (1.6 ) — — (37.7 ) Other (expense) income — — 0.4 (1.1 ) — — (0.7 ) Income (loss) before income taxes — (71.6 ) 220.2 17.1 — — 165.7 Income tax (expense) benefit (0.1 ) 20.8 (55.3 ) (4.1 ) — — (38.7 ) Income (loss) before equity in earnings of subsidiaries (0.1 ) (50.8 ) 164.9 13.0 — — 127.0 Equity in earnings of subsidiaries 127.1 177.9 — — — (305.0 ) — Net income $ 127.0 $ 127.1 $ 164.9 $ 13.0 $ — $ (305.0 ) $ 127.0 Consolidating Statement of Operations Three Months Ended March 31, 2017 (as adjusted) (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Net sales $ — $ — $ 2,886.3 $ 369.7 $ — $ — $ 3,256.0 Cost of sales — — 2,393.0 309.5 — — 2,702.5 Gross profit — — 493.3 60.2 — — 553.5 Selling and administrative expenses — 31.5 269.8 46.1 — — 347.4 Advertising expense — — 34.0 1.4 — — 35.4 Income (loss) from operations — (31.5 ) 189.5 12.7 — — 170.7 Interest (expense) income, net — (39.1 ) 1.0 (1.6 ) — — (39.7 ) Net loss on extinguishments of long-term debt — (57.4 ) — — — — (57.4 ) Other income — — 0.2 0.7 — — 0.9 Income (loss) before income taxes — (128.0 ) 190.7 11.8 — — 74.5 Income tax (expense) benefit — 57.3 (70.6 ) (3.0 ) — — (16.3 ) Income (loss) before equity in earnings of subsidiaries — (70.7 ) 120.1 8.8 — — 58.2 Equity in earnings of subsidiaries 58.2 128.9 — — — (187.1 ) — Net income $ 58.2 $ 58.2 $ 120.1 $ 8.8 $ — $ (187.1 ) $ 58.2
Condensed Statement of Comprehensive Income	Condensed Consolidating Statement of Comprehensive Income Three Months Ended March 31, 2018 (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Comprehensive income $ 144.4 $ 144.5 $ 164.9 $ 27.2 $ — $ (336.6 ) $ 144.4 Condensed Consolidating Statement of Comprehensive Income Three Months Ended March 31, 2017 (as adjusted) (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Comprehensive income $ 64.3 $ 64.3 $ 120.1 $ 15.3 $ — $ (199.7 ) $ 64.3
Condensed Consolidating Statements Cash Flows	Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2018 (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Net cash provided by (used in) operating activities $ — $ (13.8 ) $ 239.6 $ 10.8 $ — $ (14.4 ) $ 222.2 Cash flows used in investing activities: Capital expenditures — (11.1 ) (1.2 ) (3.6 ) — — (15.9 ) Net cash used in investing activities — (11.1 ) (1.2 ) (3.6 ) — — (15.9 ) Cash flows (used in) provided by financing activities: Proceeds from borrowings under revolving credit facilities — 163.0 — 7.0 — — 170.0 Repayments of borrowings under revolving credit facilities — (163.0 ) — (7.0 ) — — (170.0 ) Repayments of long-term debt — (3.7 ) — — — — (3.7 ) Net change in accounts payable-inventory financing — (0.9 ) 1.0 24.8 — — 24.9 Premium payments on interest rate cap agreements — (12.6 ) — — — — (12.6 ) Proceeds from stock option exercises — 7.3 — — — — 7.3 Proceeds from Coworker Stock Purchase Plan — 2.4 — — — — 2.4 Repurchases of common stock (109.2 ) — — — — — (109.2 ) Payment of incentive compensation plan withholding taxes (8.7 ) — — — — — (8.7 ) Dividends (32.0 ) — — — — — (32.0 ) Other — 0.7 (0.1 ) (0.2 ) — — 0.4 Distributions and advances from (to) affiliates 149.9 91.3 (239.3 ) — — (1.9 ) — Net cash (used in) provided by financing activities — 84.5 (238.4 ) 24.6 — (1.9 ) (131.2 ) Effect of exchange rate changes on cash and cash equivalents — — — 1.7 — — 1.7 Net increase in cash and cash equivalents — 59.6 — 33.5 — (16.3 ) 76.8 Cash and cash equivalents—beginning of period — 113.7 — 32.4 — (1.9 ) 144.2 Cash and cash equivalents—end of period $ — $ 173.3 $ — $ 65.9 $ — $ (18.2 ) $ 221.0 Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2017 (as adjusted) (in millions) Parent Guarantor Subsidiary Issuer Guarantor Subsidiaries Non-Guarantor Subsidiaries Co-Issuer Consolidating Adjustments Consolidated Net cash provided by operating activities $ — $ 24.5 $ 333.2 $ 38.2 $ — $ (26.0 ) $ 369.9 Cash flows from investing activities: Capital expenditures — (14.6 ) (2.4 ) (2.6 ) — — (19.6 ) Net cash used in investing activities — (14.6 ) (2.4 ) (2.6 ) — — (19.6 ) Cash flows (used in) provided by financing activities: Proceeds from borrowings under revolving credit facilities — 38.0 — 6.1 — — 44.1 Repayments of borrowings under revolving credit facilities — — — (6.1 ) — — (6.1 ) Repayments of long-term debt — (3.7 ) — — — — (3.7 ) Proceeds from issuance of long-term debt — 2,083.0 — — — — 2,083.0 Payments to extinguish long-term debt — (2,121.3 ) — — — — (2,121.3 ) Payment of debt financing fees — (9.6 ) — — — — (9.6 ) Net change in accounts payable-inventory financing — (0.9 ) (132.2 ) (2.6 ) — — (135.7 ) Proceeds from stock option exercises — 4.4 — — — — 4.4 Proceeds from Coworker Stock Purchase Plan — 2.1 — — — — 2.1 Repurchases of common stock (175.4 ) — — — — — (175.4 ) Payment of incentive compensation plan withholding taxes — (10.4 ) (7.7 ) (0.2 ) — — (18.3 ) Dividends (25.5 ) — — — — — (25.5 ) Other — — — (0.2 ) — — (0.2 ) Distributions and advances from (to) affiliates 200.9 (9.3 ) (194.0 ) — — 2.4 — Net cash used in financing activities — (27.7 ) (333.9 ) (3.0 ) — 2.4 (362.2 ) Effect of exchange rate changes on cash and cash equivalents — — — (0.1 ) — — (0.1 ) Net (decrease) increase in cash and cash equivalents — (17.8 ) (3.1 ) 32.5 — (23.6 ) (12.0 ) Cash and cash equivalents—beginning of period — 222.7 3.1 37.9 — — 263.7 Cash and cash equivalents—end of period $ — $ 204.9 $ — $ 70.4 $ — $ (23.6 ) $ 251.7

Description of Business and S30

Description of Business and Summary of Significant Accounting Policies (Details)	Mar. 31, 2018subsidiary
Accounting Policies [Abstract]
Number of owned subsidiaries	2

Recent Accounting Pronounceme31

Recent Accounting Pronouncements (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Statement Related Disclosures [Abstract]
Net sales	$ 3,606.4	$ 3,256
Gross profit	603.9	$ 553.5
Gross profit margin		17.00%
Income from operations	204.1	$ 170.7
Income tax (expense) benefit	(38.7)	(16.3)
Net income	$ 127	$ 58.2
Net income per common share:
Basic (in dollars per share)	$ 0.83	$ 0.36
Diluted (in dollars per share)	$ 0.82	$ 0.36
Balance Sheet Related Disclosures [Abstract]
Accounts receivable, net of allowance for doubtful accounts of $6.2 for both periods	$ 2,274		$ 2,329.3
Merchandise inventory	485.8		411.5
Miscellaneous receivables	310.2		343
Prepaid expenses and other	188.9		168.3
Total current assets	3,479.9		3,396.3
Other assets	47.1		32.7
Total assets	7,027.9		6,966.7
Contract liabilities	193.6		158.8
Income taxes	56.7		16.2
Other	204.9		221.8
Total current liabilities	2,582.5		2,522.1
Total liabilities			5,981.1
Total stockholders’ equity	$ 996.9		982.9
Total stockholders’ equity			985.6
As Reported
Income Statement Related Disclosures [Abstract]
Net sales		$ 3,324.7
Gross profit		$ 552.6
Gross profit margin		16.60%
Income from operations		$ 169.8
Income tax (expense) benefit		(16)
Net income		$ 57.6
Net income per common share:
Basic (in dollars per share)		$ 0.36
Diluted (in dollars per share)		$ 0.35
Balance Sheet Related Disclosures [Abstract]
Accounts receivable, net of allowance for doubtful accounts of $6.2 for both periods			2,320.5
Merchandise inventory			449.5
Miscellaneous receivables			336.5
Prepaid expenses and other			127.4
Total current assets			3,378.1
Other assets			40.8
Total assets			6,956.6
Contract liabilities			194
Income taxes			15.1
Other			180.2
Total current liabilities			2,514.6
Total liabilities			5,973.7
Total stockholders’ equity			982.9
New Revenue Standard Adjustment | Accounting Standards Update 2014-09
Income Statement Related Disclosures [Abstract]
Net sales		$ (68.7)
Gross profit		$ 0.9
Gross profit margin		0.40%
Income from operations		$ 0.9
Income tax (expense) benefit		(0.3)
Net income		$ 0.6
Net income per common share:
Basic (in dollars per share)		$ 0
Diluted (in dollars per share)		$ 0.01
Balance Sheet Related Disclosures [Abstract]
Accounts receivable, net of allowance for doubtful accounts of $6.2 for both periods			8.8
Merchandise inventory			(38)
Miscellaneous receivables			6.5
Prepaid expenses and other			40.9
Total current assets			18.2
Other assets			(8.1)
Total assets			10.1
Contract liabilities			(35.2)
Income taxes			1.1
Other			41.6
Total current liabilities			7.5
Total liabilities			7.5
Total stockholders’ equity			$ 2.7

Inventory Financing Agreement32

Inventory Financing Agreements (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Inventory Financing Agreements [Line Items]
Accounts payable-inventory financing	$ 523.7	$ 498
Accounts Payable, Inventory Financing
Inventory Financing Agreements [Line Items]
Revolving Loan inventory financing agreement	481.6	480.9
Other inventory financing agreements	$ 42.1	$ 17.1

Contract Liabilities and Rema33

Contract Liabilities and Remaining Performance Obligations - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Contract liabilities	$ 194		$ 159
Revenue recognized from contract with customer	$ 58	$ 45

Contract Liabilities and Rema34

Contract Liabilities and Remaining Performance Obligations - Schedule of Remaining Performance Obligations (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, expected timing of satisfaction, period	1 year
Remaining Performance Obligations	$ 39.2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, expected timing of satisfaction, period	1 year
Remaining Performance Obligations	$ 25.6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, expected timing of satisfaction, period	1 year
Remaining Performance Obligations	$ 9.6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, expected timing of satisfaction, period
Remaining Performance Obligations	$ 0.7

Financial Instruments (Details)

Financial Instruments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative [Line Items]
Premium payments on interest rate cap agreements	$ 12.6	$ 0
Cap agreement effective 12/31/18-12/31/20
Derivative [Line Items]
Notional amount	1,400
Interest Rate Contract
Derivative [Line Items]
Unrealized gain on effective portion of interest rate cap agreements	3
Tax expense	1
Amount to be reclassified from AOCL to interest expense	5
Derivative
Derivative [Line Items]
Interest gain (loss) reclassified to earnings (less than)	$ 1	$ 1

Financial Instruments - Schedul

Financial Instruments - Schedule of Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Interest rate cap, fair value	$ 21.5	$ 5.4
Cap agreement effective 1/1/17-12/31/18 [Member]
Derivative [Line Items]
Notional amount	1,400
Interest rate cap, fair value		5.4
Cap agreement effective 1/17/18-12/31/18 [Member]
Derivative [Line Items]
Interest rate cap, fair value	8.8
Cap agreement effective 12/31/18-12/31/20
Derivative [Line Items]
Notional amount	1,400
Interest rate cap, fair value	$ 12.7	$ 0

Long-Term Debt - Debt Balances

Long-Term Debt - Debt Balances and Interest Rates (Details) £ in Millions	Mar. 31, 2018GBP (£)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Principal		$ 3,255,000,000	$ 3,255,900,000
Long-term debt, current maturities, gross		(25,800,000)	(25,500,000)
Long-term debt, excluding current maturities, gross		3,229,200,000	3,230,400,000
Deferred finance costs, net		(19,500,000)	(20,400,000)
Deferred finance costs, current, net		0	0
Deferred financing costs, noncurrent, net		(19,500,000)	(20,400,000)
Long-term debt, net of deferred financing costs		3,235,500,000	3,235,500,000
Current maturities of long-term debt, net of Deferred financing costs		(25,800,000)	(25,500,000)
Long-term debt, excluding current maturities, net of deferred financing costs		$ 3,209,700,000	$ 3,210,000,000
Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Interest Rate	0.00%	0.00%	0.00%
Principal		$ 0	$ 0
Deferred finance costs, net		0	0
Long-term debt, net of deferred financing costs		$ 0	$ 0
CDW UK revolving credit facility
Debt Instrument [Line Items]
Interest Rate	0.00%	0.00%	0.00%
Principal		$ 0	$ 0
Deferred finance costs, net		0	0
Long-term debt, net of deferred financing costs		$ 0	$ 0
Senior secured term loan facility
Debt Instrument [Line Items]
Interest Rate	4.30%	4.30%	3.70%
Principal		$ 1,464,300,000	$ 1,468,000,000	$ 1,500,000,000
Deferred finance costs, net		(2,000,000)	(2,000,000)
Long-term debt, net of deferred financing costs		$ 1,462,300,000	$ 1,466,000,000
CDW UK term loan
Debt Instrument [Line Items]
Interest Rate	1.98%	1.98%	1.92%
Principal	£ 56	$ 78,500,000	$ 75,700,000
Deferred finance costs, net		(1,300,000)	(1,400,000)
Long-term debt, net of deferred financing costs		$ 77,200,000	$ 74,300,000
Senior notes due 2023
Debt Instrument [Line Items]
Interest Rate	5.00%	5.00%	5.00%
Principal		$ 525,000,000	$ 525,000,000
Deferred finance costs, net		(4,200,000)	(4,500,000)
Long-term debt, net of deferred financing costs		$ 520,800,000	$ 520,500,000
Senior notes due 2024
Debt Instrument [Line Items]
Interest Rate	5.50%	5.50%	5.50%
Principal		$ 575,000,000	$ 575,000,000
Deferred finance costs, net		(5,000,000)	(5,200,000)
Long-term debt, net of deferred financing costs		$ 570,000,000	$ 569,800,000
Senior notes due 2025
Debt Instrument [Line Items]
Interest Rate	5.00%	5.00%	5.00%
Principal		$ 600,000,000	$ 600,000,000
Deferred finance costs, net		(7,000,000)	(7,300,000)
Long-term debt, net of deferred financing costs		593,000,000	592,700,000
Other long-term obligations
Debt Instrument [Line Items]
Principal		12,200,000	12,200,000
Deferred finance costs, net		0	0
Long-term debt, net of deferred financing costs		$ 12,200,000	$ 12,200,000

Long-Term Debt - Revolving Loan

Long-Term Debt - Revolving Loan (Details) £ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	Mar. 31, 2018GBP (£)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Carrying value				$ 3,255,000,000	$ 3,255,900,000
Net loss on extinguishments of long-term debt	$ 0	$ 57,400,000
CDW UK term loan
Debt Instrument [Line Items]
Carrying value			£ 56	78,500,000	75,700,000
Deferred finance costs, net and unamortized premium			£ 1	1,000,000
Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Carrying value				0	$ 0
Undrawn letters of credit				1,000,000
Borrowing base				1,600,000,000
Additional borrowing capacity				987,000,000
Cash availability, minimum liquidity				$ 125,000,000
Cash availability, percentage of borrowing base			10.00%	10.00%
Minimum liquidity, amount				$ 100,000,000
Basis spread on variable rate (as percent)	1.00%
Net loss on extinguishments of long-term debt		1,000,000
Deferred finance costs, net and unamortized premium		$ 4,000,000
Minimum | Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Consolidated fixed charge coverage ratio			1	1
Federal Funds Effective Swap Rate | Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Basis spread on variable rate (as percent)	0.50%
London Interbank Offered Rate (LIBOR) | Minimum | Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Basis spread on variable rate (as percent)	1.25%
London Interbank Offered Rate (LIBOR) | Maximum | Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Basis spread on variable rate (as percent)	1.75%
Base Rate | Minimum | Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Basis spread on variable rate (as percent)	0.25%
Base Rate | Maximum | Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Basis spread on variable rate (as percent)	0.75%
Accounts Payable, Inventory Financing | Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Amount owed under Revolving loan financing agreement				$ 462,000,000

Long-Term Debt - Term Loan (Det

Long-Term Debt - Term Loan (Details) £ in Millions, $ in Millions	3 Months Ended
	Sep. 30, 2018GBP (£)	Sep. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	Mar. 31, 2018GBP (£)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Carrying value						$ 3,255	$ 3,255.9
Net loss on extinguishments of long-term debt			$ 0	$ 57.4
Senior secured term loan facility
Debt Instrument [Line Items]
Carrying value						1,464.3	$ 1,468	$ 1,500
Deferred financing costs						$ 2
Quarterly principal installment			$ 4
Net loss on extinguishments of long-term debt				14
Write off of deferred financing costs				5
Write off of deferred debt discount				9
Payments of debt issuance costs				$ 2
Interest Rate					4.30%	4.30%	3.70%
CDW UK term loan
Debt Instrument [Line Items]
Carrying value					£ 56	$ 78.5	$ 75.7
Variable interest rate margin					1.40%	1.40%
Deferred finance costs, net and unamortized premium					£ (1)	$ (1)
Interest Rate					1.98%	1.98%	1.92%
CDW UK Revolving Credit Facility
Debt Instrument [Line Items]
Carrying value | £					£ 0
Additional borrowing capacity					£ 50	$ 70
ABR | Senior secured term loan facility
Debt Instrument [Line Items]
Variable interest rate margin					1.00%	1.00%
LIBOR | Senior secured term loan facility
Debt Instrument [Line Items]
Variable interest rate margin					2.00%	2.00%
Scenario, Forecast | CDW UK term loan
Debt Instrument [Line Items]
Repayments of debt	£ 5	$ 7

Long-Term Debt - Senior Notes (

Long-Term Debt - Senior Notes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Debt Instrument [Line Items]
Carrying value	$ 3,255		$ 3,255.9
Net loss on extinguishments of long-term debt	0	$ (57.4)
Deferred finance costs, net	19.5		20.4
Senior notes due 2023
Debt Instrument [Line Items]
Carrying value	$ 525		$ 525
Interest Rate	5.00%		5.00%
Deferred finance costs, net	$ 4.2		$ 4.5
Senior notes due 2024
Debt Instrument [Line Items]
Carrying value	$ 575		$ 575
Interest Rate	5.50%		5.50%
Deferred finance costs, net	$ 5		$ 5.2
Senior notes due 2025
Debt Instrument [Line Items]
Carrying value	$ 600		$ 600
Interest Rate	5.00%		5.00%
Deferred finance costs, net	$ 7		$ 7.3
Senior notes due 2022
Debt Instrument [Line Items]
Carrying value		600
Net loss on extinguishments of long-term debt		(43)
Redemption premium		37
Deferred finance costs, net and unamortized premium		$ (6)

Long-Term Debt - Debt Covenants

Long-Term Debt - Debt Covenants (Details) £ in Millions, $ in Millions	Mar. 31, 2018GBP (£)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 3,255	$ 3,255.9
Senior secured term loan facility
Debt Instrument [Line Items]
Long-term Debt, Gross		1,464.3	1,468	$ 1,500
Amount of restricted payment capacity		$ 1,200
Net leverage ratio	2.49	2.49
CDW UK term loan
Debt Instrument [Line Items]
Long-term Debt, Gross	£ 56	$ 78.5	$ 75.7
Amount of restricted payment capacity	£ 99	$ 139

Long-Term Debt - Fair Value of

Long-Term Debt - Fair Value of Long-Term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value [Line Items]
Carrying value	$ 3,255	$ 3,255.9
Fair Value, Inputs, Level 2
Fair Value [Line Items]
Long-term debt, fair value disclosures	$ 3,290.7	$ 3,366.5

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense	$ 38.7	$ 16.3
Effective income tax rate reconciliation, percent	23.40%	21.90%

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details)	Feb. 14, 2018shares
Equity [Abstract]
Treasury stock retired (in shares)	109,207

Earnings per Share (Details)

Earnings per Share (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Basic weighted-average shares outstanding (in shares)	152.2	159.4
Effect of dilutive securities	2.6	3.4
Diluted weighted-average shares outstanding (in shares)	154.8	162.8
Anti-dilutive shares (less than) (in shares)	1	1

Segment Information - Narrative

Segment Information - Narrative (Details)	3 Months Ended
	Mar. 31, 2018employeesegment
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Number of operating segments which do not meet reportable unit quantitative threshold | segment	2
Minimum | Corporate
Segment Reporting Information [Line Items]
Customer segments, customer employee headcount | employee	250
Maximum | Small Business
Segment Reporting Information [Line Items]
Customer segments, customer employee headcount | employee	250

Segment Information - Schedule

Segment Information - Schedule of Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Net sales	$ 3,606.4	$ 3,256
Income (loss) from operations	204.1	170.7
Depreciation and amortization expense	(66.6)	(64.2)
Operating Segments | Corporate
Segment Reporting Information [Line Items]
Net sales	1,565.8	1,440.6
Income (loss) from operations	124.8	112.1
Depreciation and amortization expense	(21.1)	(20.8)
Operating Segments | Small Business
Segment Reporting Information [Line Items]
Net sales	327.6	292
Income (loss) from operations	22.3	16.6
Depreciation and amortization expense	(5.2)	(5.1)
Operating Segments | Public
Segment Reporting Information [Line Items]
Net sales	1,230	1,153.7
Income (loss) from operations	71.7	60.8
Depreciation and amortization expense	(11.2)	(11.2)
Operating Segments | Other
Segment Reporting Information [Line Items]
Net sales	483	369.7
Income (loss) from operations	19.8	12.7
Depreciation and amortization expense	(8.8)	(7.2)
Headquarters
Segment Reporting Information [Line Items]
Net sales	0	0
Income (loss) from operations	(34.5)	(31.5)
Depreciation and amortization expense	$ (20.3)	$ (19.9)

Segment Information - Disaggreg

Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Net sales	$ 3,606.4	$ 3,256
Revenue net, by Product and Service, Percentage	100.00%	100.00%
Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	$ 1,565.8	$ 1,440.6
Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	327.6	292
Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	1,230	1,153.7
Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	483	369.7
Transferred at a point in time where CDW is principal
Disaggregation of Revenue [Line Items]
Net sales	3,340.1	3,027.2
Transferred at a point in time where CDW is principal | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	1,426.3	1,314.2
Transferred at a point in time where CDW is principal | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	309.4	275.7
Transferred at a point in time where CDW is principal | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	1,171.4	1,105.8
Transferred at a point in time where CDW is principal | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	433	331.5
Transferred at a point in time where CDW is agent
Disaggregation of Revenue [Line Items]
Net sales	165.4	141
Transferred at a point in time where CDW is agent | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	92.7	81.3
Transferred at a point in time where CDW is agent | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	16.5	14
Transferred at a point in time where CDW is agent | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	41.1	37.5
Transferred at a point in time where CDW is agent | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	15.1	8.2
Transferred over time where CDW is principal
Disaggregation of Revenue [Line Items]
Net sales	100.9	87.8
Transferred over time where CDW is principal | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	46.8	45.1
Transferred over time where CDW is principal | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	1.7	2.3
Transferred over time where CDW is principal | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	17.5	10.4
Transferred over time where CDW is principal | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	34.9	30
Corporate
Disaggregation of Revenue [Line Items]
Net sales	1,565.8	1,440.6
Corporate | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	1,565.8	1,440.6
Corporate | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Corporate | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	0	0
Corporate | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	0	0
Small Business
Disaggregation of Revenue [Line Items]
Net sales	327.6	292
Small Business | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	0	0
Small Business | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	327.6	292
Small Business | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	0	0
Small Business | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	0	0
Government
Disaggregation of Revenue [Line Items]
Net sales	418.5	374.6
Government | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	0	0
Government | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Government | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	418.5	374.6
Government | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	0	0
Education
Disaggregation of Revenue [Line Items]
Net sales	397.2	393.2
Education | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	0	0
Education | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Education | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	397.2	393.2
Education | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	0	0
Healthcare
Disaggregation of Revenue [Line Items]
Net sales	414.3	385.9
Healthcare | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	0	0
Healthcare | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Healthcare | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	414.3	385.9
Healthcare | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	0	0
Other
Disaggregation of Revenue [Line Items]
Net sales	483	369.7
Other | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	0	0
Other | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Other | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	0	0
Other | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	483	369.7
Notebooks/Mobile Devices
Disaggregation of Revenue [Line Items]
Net sales	$ 858.7	$ 735.5
Revenue net, by Product and Service, Percentage	23.80%	22.60%
Netcomm Products
Disaggregation of Revenue [Line Items]
Net sales	$ 482.9	$ 458.6
Revenue net, by Product and Service, Percentage	13.40%	14.10%
Desktops
Disaggregation of Revenue [Line Items]
Net sales	$ 303.5	$ 263.2
Revenue net, by Product and Service, Percentage	8.40%	8.10%
Video
Disaggregation of Revenue [Line Items]
Net sales	$ 259.2	$ 235.7
Revenue net, by Product and Service, Percentage	7.20%	7.20%
Enterprise and Data Storage (Including Drives)
Disaggregation of Revenue [Line Items]
Net sales	$ 256	$ 234.8
Revenue net, by Product and Service, Percentage	7.10%	7.20%
Other Hardware
Disaggregation of Revenue [Line Items]
Net sales	$ 751.8	$ 711.6
Revenue net, by Product and Service, Percentage	20.80%	21.90%
Hardware
Disaggregation of Revenue [Line Items]
Net sales	$ 2,912.1	$ 2,639.4
Revenue net, by Product and Service, Percentage	80.70%	81.10%
Hardware | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	$ 1,251.6	$ 1,146.5
Hardware | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	272.8	240.8
Hardware | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	1,008.2	958.6
Hardware | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	379.5	293.5
Software
Disaggregation of Revenue [Line Items]
Net sales	$ 505.1	$ 447.9
Revenue net, by Product and Service, Percentage	14.00%	13.80%
Software | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	$ 219.6	$ 202
Software | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	43.1	39.9
Software | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	183.1	162.8
Software | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	59.3	43.2
Services
Disaggregation of Revenue [Line Items]
Net sales	$ 161.2	$ 141.3
Revenue net, by Product and Service, Percentage	4.50%	4.30%
Services | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	$ 78.1	$ 75.8
Services | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	6.3	6.2
Services | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	34.6	28
Services | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	42.2	31.3
Other
Disaggregation of Revenue [Line Items]
Net sales	$ 28	$ 27.4
Revenue net, by Product and Service, Percentage	0.80%	0.80%
Other | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	$ 16.5	$ 16.3
Other | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	5.4	5.1
Other | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	4.1	4.3
Other | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	2	1.7
United States
Disaggregation of Revenue [Line Items]
Net sales	3,131.2	2,891.3
United States | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	1,564.4	1,439.5
United States | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	327.6	292
United States | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	1,230	1,153.7
United States | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	9.2	6.1
Rest of World
Disaggregation of Revenue [Line Items]
Net sales	475.2	364.7
Rest of World | Operating Segments | Corporate
Disaggregation of Revenue [Line Items]
Net sales	1.4	1.1
Rest of World | Operating Segments | Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Rest of World | Operating Segments | Public
Disaggregation of Revenue [Line Items]
Net sales	0	0
Rest of World | Operating Segments | Other
Disaggregation of Revenue [Line Items]
Net sales	$ 473.8	$ 363.6

Supplemental Guarantor Inform49

Supplemental Guarantor Information - Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 221	$ 144.2	$ 251.7	$ 263.7
Accounts receivable, net	2,274	2,329.3
Merchandise inventory	485.8	411.5
Miscellaneous receivables	310.2	343
Prepaid expenses and other	188.9	168.3
Total current assets	3,479.9	3,396.3
Property and equipment, net	153.1	161.1
Goodwill	2,488.8	2,479.6
Other intangible assets, net	859	897
Other assets	47.1	32.7
Investment in and advances to subsidiaries	0	0
Total Assets	7,027.9	6,966.7
Current liabilities:
Accounts payable-trade	1,288.5	1,317.7
Accounts payable-inventory financing	523.7	498
Current maturities of long-term debt	25.8	25.5
Contract liabilities	193.6	158.8
Accrued expenses and other current liabilities	550.9	522.1
Total current liabilities	2,582.5	2,522.1
Long-term liabilities:
Debt	3,209.7	3,210
Deferred income taxes	188.9	196.3
Other liabilities	49.9	52.7
Total long-term liabilities	3,448.5	3,459
Total stockholders' equity	996.9	982.9
Total stockholders' equity		985.6
Total Liabilities and Stockholders' Equity	7,027.9	6,966.7
Consolidating Adjustments
Current assets:
Cash and cash equivalents	(18.2)	(1.9)	(23.6)	0
Accounts receivable, net	0	0
Merchandise inventory	0	0
Miscellaneous receivables	0	0
Prepaid expenses and other	0	0
Total current assets	(18.2)	(1.9)
Property and equipment, net	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other assets	(216.9)	(211.6)
Investment in and advances to subsidiaries	(4,012.1)	(4,050)
Total Assets	(4,247.2)	(4,263.5)
Current liabilities:
Accounts payable-trade	(18.2)	(1.9)
Accounts payable-inventory financing	0	0
Current maturities of long-term debt	0	0
Contract liabilities	0	0
Accrued expenses and other current liabilities	0	0
Total current liabilities	(18.2)	(1.9)
Long-term liabilities:
Debt	0	0
Deferred income taxes	(1.6)	(1.7)
Other liabilities	(215.3)	(209.9)
Total long-term liabilities	(216.9)	(211.6)
Total stockholders' equity	(4,012.1)
Total stockholders' equity		(4,050)
Total Liabilities and Stockholders' Equity	(4,247.2)	(4,263.5)
Parent Guarantor | Reportable Legal Entities
Current assets:
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	0	0
Merchandise inventory	0	0
Miscellaneous receivables	0	0
Prepaid expenses and other	0	0
Total current assets	0	0
Property and equipment, net	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other assets	1.6	1.7
Investment in and advances to subsidiaries	995.3	983.9
Total Assets	996.9	985.6
Current liabilities:
Accounts payable-trade	0	0
Accounts payable-inventory financing	0	0
Current maturities of long-term debt	0	0
Contract liabilities	0	0
Accrued expenses and other current liabilities	0	0
Total current liabilities	0	0
Long-term liabilities:
Debt	0	0
Deferred income taxes	0	0
Other liabilities	0	0
Total long-term liabilities	0	0
Total stockholders' equity	996.9
Total stockholders' equity		985.6
Total Liabilities and Stockholders' Equity	996.9	985.6
Subsidiary Issuer | Reportable Legal Entities
Current assets:
Cash and cash equivalents	173.3	113.7	204.9	222.7
Accounts receivable, net	0	0
Merchandise inventory	0	0
Miscellaneous receivables	105.2	103.9
Prepaid expenses and other	21.5	18
Total current assets	300	235.6
Property and equipment, net	87.7	95
Goodwill	751.8	751.8
Other intangible assets, net	277.4	280.1
Other assets	52.1	30.7
Investment in and advances to subsidiaries	3,016.8	3,066.1
Total Assets	4,485.8	4,459.3
Current liabilities:
Accounts payable-trade	24.6	42.5
Accounts payable-inventory financing	0	1
Current maturities of long-term debt	14.9	14.9
Contract liabilities	0	0
Accrued expenses and other current liabilities	210.6	173.3
Total current liabilities	250.1	231.7
Long-term liabilities:
Debt	3,131.2	3,134.2
Deferred income taxes	69	66.5
Other liabilities	40.2	43
Total long-term liabilities	3,240.4	3,243.7
Total stockholders' equity	995.3
Total stockholders' equity		983.9
Total Liabilities and Stockholders' Equity	4,485.8	4,459.3
Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash and cash equivalents	0	0	0	3.1
Accounts receivable, net	1,898.8	2,015.7
Merchandise inventory	401	354.6
Miscellaneous receivables	182.7	211.1
Prepaid expenses and other	119.9	100.4
Total current assets	2,602.4	2,681.8
Property and equipment, net	42.1	43.5
Goodwill	1,439	1,439
Other intangible assets, net	388.6	424.5
Other assets	207.5	209.3
Investment in and advances to subsidiaries	0	0
Total Assets	4,679.6	4,798.1
Current liabilities:
Accounts payable-trade	1,063.6	1,112.1
Accounts payable-inventory financing	481.8	480.9
Current maturities of long-term debt	3.8	3.8
Contract liabilities	100.4	87.5
Accrued expenses and other current liabilities	263.4	262
Total current liabilities	1,913	1,946.3
Long-term liabilities:
Debt	8.3	8.3
Deferred income taxes	89.3	100.1
Other liabilities	4.9	4.7
Total long-term liabilities	102.5	113.1
Total stockholders' equity	2,664.1
Total stockholders' equity		2,738.7
Total Liabilities and Stockholders' Equity	4,679.6	4,798.1
Non-Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash and cash equivalents	65.9	32.4	70.4	37.9
Accounts receivable, net	375.2	313.6
Merchandise inventory	84.8	56.9
Miscellaneous receivables	22.3	28
Prepaid expenses and other	47.5	49.9
Total current assets	595.7	480.8
Property and equipment, net	23.3	22.6
Goodwill	298	288.8
Other intangible assets, net	193	192.4
Other assets	2.8	2.6
Investment in and advances to subsidiaries	0	0
Total Assets	1,112.8	987.2
Current liabilities:
Accounts payable-trade	218.5	165
Accounts payable-inventory financing	41.9	16.1
Current maturities of long-term debt	7.1	6.8
Contract liabilities	93.2	71.3
Accrued expenses and other current liabilities	76.9	86.8
Total current liabilities	437.6	346
Long-term liabilities:
Debt	70.2	67.5
Deferred income taxes	32.2	31.4
Other liabilities	220.1	214.9
Total long-term liabilities	322.5	313.8
Total stockholders' equity	352.7
Total stockholders' equity		327.4
Total Liabilities and Stockholders' Equity	1,112.8	987.2
Co-Issuer | Reportable Legal Entities
Current assets:
Cash and cash equivalents	0	0	$ 0	$ 0
Accounts receivable, net	0	0
Merchandise inventory	0	0
Miscellaneous receivables	0	0
Prepaid expenses and other	0	0
Total current assets	0	0
Property and equipment, net	0	0
Goodwill	0	0
Other intangible assets, net	0	0
Other assets	0	0
Investment in and advances to subsidiaries	0	0
Total Assets	0	0
Current liabilities:
Accounts payable-trade	0	0
Accounts payable-inventory financing	0	0
Current maturities of long-term debt	0	0
Contract liabilities	0	0
Accrued expenses and other current liabilities	0	0
Total current liabilities	0	0
Long-term liabilities:
Debt	0	0
Deferred income taxes	0	0
Other liabilities	0	0
Total long-term liabilities	0	0
Total stockholders' equity	0
Total stockholders' equity		0
Total Liabilities and Stockholders' Equity	$ 0	$ 0

Supplemental Guarantor Inform50

Supplemental Guarantor Information - Consolidating Statements of Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Supplemental Guarantor Information [Line Items]
Net sales	$ 3,606.4	$ 3,256
Cost of sales	3,002.5	2,702.5
Gross profit	603.9	553.5
Selling and administrative expenses	362.7	347.4
Advertising expense	37.1	35.4
Income from operations	204.1	170.7
Interest expense, net	(37.7)	(39.7)
Net loss on extinguishments of long-term debt	0	(57.4)
Other (expense) income	(0.7)	0.9
Income before income taxes	165.7	74.5
Income tax (expense) benefit	(38.7)	(16.3)
Income (loss) before equity in earnings of subsidiaries	127	58.2
Equity in earnings of subsidiaries	0	0
Net income	127	58.2
Consolidating Adjustments
Supplemental Guarantor Information [Line Items]
Net sales	0	0
Cost of sales	0	0
Gross profit	0	0
Selling and administrative expenses	0	0
Advertising expense	0	0
Income from operations	0	0
Interest expense, net	0	0
Net loss on extinguishments of long-term debt		0
Other (expense) income	0	0
Income before income taxes	0	0
Income tax (expense) benefit	0	0
Income (loss) before equity in earnings of subsidiaries	0	0
Equity in earnings of subsidiaries	(305)	(187.1)
Net income	(305)	(187.1)
Parent Guarantor | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Net sales	0	0
Cost of sales	0	0
Gross profit	0	0
Selling and administrative expenses	0	0
Advertising expense	0	0
Income from operations	0	0
Interest expense, net	0	0
Net loss on extinguishments of long-term debt		0
Other (expense) income	0	0
Income before income taxes	0	0
Income tax (expense) benefit	(0.1)	0
Income (loss) before equity in earnings of subsidiaries	(0.1)	0
Equity in earnings of subsidiaries	127.1	58.2
Net income	127	58.2
Subsidiary Issuer | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Net sales	0	0
Cost of sales	0	0
Gross profit	0	0
Selling and administrative expenses	34.5	31.5
Advertising expense	0	0
Income from operations	(34.5)	(31.5)
Interest expense, net	(37.1)	(39.1)
Net loss on extinguishments of long-term debt		(57.4)
Other (expense) income	0	0
Income before income taxes	(71.6)	(128)
Income tax (expense) benefit	20.8	57.3
Income (loss) before equity in earnings of subsidiaries	(50.8)	(70.7)
Equity in earnings of subsidiaries	177.9	128.9
Net income	127.1	58.2
Guarantor Subsidiaries | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Net sales	3,123.4	2,886.3
Cost of sales	2,597	2,393
Gross profit	526.4	493.3
Selling and administrative expenses	272.4	269.8
Advertising expense	35.2	34
Income from operations	218.8	189.5
Interest expense, net	1	1
Net loss on extinguishments of long-term debt		0
Other (expense) income	0.4	0.2
Income before income taxes	220.2	190.7
Income tax (expense) benefit	(55.3)	(70.6)
Income (loss) before equity in earnings of subsidiaries	164.9	120.1
Equity in earnings of subsidiaries	0	0
Net income	164.9	120.1
Non-Guarantor Subsidiaries | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Net sales	483	369.7
Cost of sales	405.5	309.5
Gross profit	77.5	60.2
Selling and administrative expenses	55.8	46.1
Advertising expense	1.9	1.4
Income from operations	19.8	12.7
Interest expense, net	(1.6)	(1.6)
Net loss on extinguishments of long-term debt		0
Other (expense) income	(1.1)	0.7
Income before income taxes	17.1	11.8
Income tax (expense) benefit	(4.1)	(3)
Income (loss) before equity in earnings of subsidiaries	13	8.8
Equity in earnings of subsidiaries	0	0
Net income	13	8.8
Co-Issuer | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Net sales	0	0
Cost of sales	0	0
Gross profit	0	0
Selling and administrative expenses	0	0
Advertising expense	0	0
Income from operations	0	0
Interest expense, net	0	0
Net loss on extinguishments of long-term debt		0
Other (expense) income	0	0
Income before income taxes	0	0
Income tax (expense) benefit	0	0
Income (loss) before equity in earnings of subsidiaries	0	0
Equity in earnings of subsidiaries	0	0
Net income	$ 0	$ 0

Supplemental Guarantor Inform51

Supplemental Guarantor Information - Condensed Consolidating Statements of Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Supplemental Guarantor Information [Line Items]
Comprehensive income (loss)	$ 144.4	$ 64.3
Consolidating Adjustments
Supplemental Guarantor Information [Line Items]
Comprehensive income (loss)	(336.6)	(199.7)
Parent Guarantor | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Comprehensive income (loss)	144.4	64.3
Subsidiary Issuer | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Comprehensive income (loss)	144.5	64.3
Guarantor Subsidiaries | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Comprehensive income (loss)	164.9	120.1
Non-Guarantor Subsidiaries | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Comprehensive income (loss)	27.2	15.3
Co-Issuer | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Comprehensive income (loss)	$ 0	$ 0

Supplemental Guarantor Inform52

Supplemental Guarantor Information - Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	$ 222.2	$ 369.9
Cash flows used in investing activities:
Capital expenditures	(15.9)	(19.6)
Net cash used in investing activities	(15.9)	(19.6)
Cash flows used in financing activities:
Proceeds from borrowings under revolving credit facilities	170	44.1
Repayments of borrowings under revolving credit facilities	(170)	(6.1)
Repayments of long-term debt	(3.7)	(3.7)
Proceeds from issuance of long-term debt	0	2,083
Payments to extinguish long-term debt	0	(2,121.3)
Payments of debt financing costs	0	(9.6)
Net change in accounts payable-inventory financing	24.9	(135.7)
Premium payments on interest rate cap agreements	(12.6)	0
Proceeds from stock option exercises	7.3	4.4
Proceeds from Coworker Stock Purchase Plan	2.4	2.1
Repurchases of common stock	(109.2)	(175.4)
Payment of incentive compensation plan withholding taxes	(8.7)	(18.3)
Dividends	(32)	(25.5)
Other	0.4	(0.2)
Distributions and advances from (to) affiliates	0	0
Net cash used in financing activities	(131.2)	(362.2)
Effect of exchange rate changes on cash and cash equivalents	1.7	(0.1)
Net increase (decrease) in cash and cash equivalents	76.8	(12)
Cash and cash equivalents—beginning of period	144.2	263.7
Cash and cash equivalents—end of period	221	251.7
Consolidating Adjustments
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	(14.4)	(26)
Cash flows used in investing activities:
Capital expenditures	0	0
Net cash used in investing activities	0	0
Cash flows used in financing activities:
Proceeds from borrowings under revolving credit facilities	0	0
Repayments of borrowings under revolving credit facilities	0	0
Repayments of long-term debt	0	0
Proceeds from issuance of long-term debt		0
Payments to extinguish long-term debt		0
Payments of debt financing costs		0
Net change in accounts payable-inventory financing	0	0
Premium payments on interest rate cap agreements	0
Proceeds from stock option exercises	0	0
Proceeds from Coworker Stock Purchase Plan	0	0
Repurchases of common stock	0	0
Payment of incentive compensation plan withholding taxes	0	0
Dividends	0	0
Other	0	0
Distributions and advances from (to) affiliates	(1.9)	2.4
Net cash used in financing activities	(1.9)	2.4
Effect of exchange rate changes on cash and cash equivalents	0	0
Net increase (decrease) in cash and cash equivalents	(16.3)	(23.6)
Cash and cash equivalents—beginning of period	(1.9)	0
Cash and cash equivalents—end of period	(18.2)	(23.6)
Parent Guarantor | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	0	0
Cash flows used in investing activities:
Capital expenditures	0	0
Net cash used in investing activities	0	0
Cash flows used in financing activities:
Proceeds from borrowings under revolving credit facilities	0	0
Repayments of borrowings under revolving credit facilities	0	0
Repayments of long-term debt	0	0
Proceeds from issuance of long-term debt		0
Payments to extinguish long-term debt		0
Payments of debt financing costs		0
Net change in accounts payable-inventory financing	0	0
Premium payments on interest rate cap agreements	0
Proceeds from stock option exercises	0	0
Proceeds from Coworker Stock Purchase Plan	0	0
Repurchases of common stock	(109.2)	(175.4)
Payment of incentive compensation plan withholding taxes	(8.7)	0
Dividends	(32)	(25.5)
Other	0	0
Distributions and advances from (to) affiliates	149.9	200.9
Net cash used in financing activities	0	0
Effect of exchange rate changes on cash and cash equivalents	0	0
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents—beginning of period	0	0
Cash and cash equivalents—end of period	0	0
Subsidiary Issuer | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	(13.8)	24.5
Cash flows used in investing activities:
Capital expenditures	(11.1)	(14.6)
Net cash used in investing activities	(11.1)	(14.6)
Cash flows used in financing activities:
Proceeds from borrowings under revolving credit facilities	163	38
Repayments of borrowings under revolving credit facilities	(163)	0
Repayments of long-term debt	(3.7)	(3.7)
Proceeds from issuance of long-term debt		2,083
Payments to extinguish long-term debt		(2,121.3)
Payments of debt financing costs		(9.6)
Net change in accounts payable-inventory financing	(0.9)	(0.9)
Premium payments on interest rate cap agreements	(12.6)
Proceeds from stock option exercises	7.3	4.4
Proceeds from Coworker Stock Purchase Plan	2.4	2.1
Repurchases of common stock	0	0
Payment of incentive compensation plan withholding taxes	0	(10.4)
Dividends	0	0
Other	0.7	0
Distributions and advances from (to) affiliates	91.3	(9.3)
Net cash used in financing activities	84.5	(27.7)
Effect of exchange rate changes on cash and cash equivalents	0	0
Net increase (decrease) in cash and cash equivalents	59.6	(17.8)
Cash and cash equivalents—beginning of period	113.7	222.7
Cash and cash equivalents—end of period	173.3	204.9
Guarantor Subsidiaries
Cash flows used in financing activities:
Payments of debt financing costs		0
Guarantor Subsidiaries | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	239.6	333.2
Cash flows used in investing activities:
Capital expenditures	(1.2)	(2.4)
Net cash used in investing activities	(1.2)	(2.4)
Cash flows used in financing activities:
Proceeds from borrowings under revolving credit facilities	0	0
Repayments of borrowings under revolving credit facilities	0	0
Repayments of long-term debt	0	0
Proceeds from issuance of long-term debt		0
Payments to extinguish long-term debt		0
Net change in accounts payable-inventory financing	1	(132.2)
Premium payments on interest rate cap agreements	0
Proceeds from stock option exercises	0	0
Proceeds from Coworker Stock Purchase Plan	0	0
Repurchases of common stock	0	0
Payment of incentive compensation plan withholding taxes	0	(7.7)
Dividends	0	0
Other	(0.1)	0
Distributions and advances from (to) affiliates	(239.3)	(194)
Net cash used in financing activities	(238.4)	(333.9)
Effect of exchange rate changes on cash and cash equivalents	0	0
Net increase (decrease) in cash and cash equivalents	0	(3.1)
Cash and cash equivalents—beginning of period	0	3.1
Cash and cash equivalents—end of period	0	0
Non-Guarantor Subsidiaries | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	10.8	38.2
Cash flows used in investing activities:
Capital expenditures	(3.6)	(2.6)
Net cash used in investing activities	(3.6)	(2.6)
Cash flows used in financing activities:
Proceeds from borrowings under revolving credit facilities	7	6.1
Repayments of borrowings under revolving credit facilities	(7)	(6.1)
Repayments of long-term debt	0	0
Proceeds from issuance of long-term debt		0
Payments to extinguish long-term debt		0
Payments of debt financing costs		0
Net change in accounts payable-inventory financing	24.8	(2.6)
Premium payments on interest rate cap agreements	0
Proceeds from stock option exercises	0	0
Proceeds from Coworker Stock Purchase Plan	0	0
Repurchases of common stock	0	0
Payment of incentive compensation plan withholding taxes	0	(0.2)
Dividends	0	0
Other	(0.2)	(0.2)
Distributions and advances from (to) affiliates	0	0
Net cash used in financing activities	24.6	(3)
Effect of exchange rate changes on cash and cash equivalents	1.7	(0.1)
Net increase (decrease) in cash and cash equivalents	33.5	32.5
Cash and cash equivalents—beginning of period	32.4	37.9
Cash and cash equivalents—end of period	65.9	70.4
Co-Issuer | Reportable Legal Entities
Supplemental Guarantor Information [Line Items]
Net cash provided by operating activities	0	0
Cash flows used in investing activities:
Capital expenditures	0	0
Net cash used in investing activities	0	0
Cash flows used in financing activities:
Proceeds from borrowings under revolving credit facilities	0	0
Repayments of borrowings under revolving credit facilities	0	0
Repayments of long-term debt	0	0
Proceeds from issuance of long-term debt		0
Payments to extinguish long-term debt		0
Payments of debt financing costs		0
Net change in accounts payable-inventory financing	0	0
Premium payments on interest rate cap agreements	0
Proceeds from stock option exercises	0	0
Proceeds from Coworker Stock Purchase Plan	0	0
Repurchases of common stock	0	0
Payment of incentive compensation plan withholding taxes	0	0
Dividends	0	0
Other	0	0
Distributions and advances from (to) affiliates	0	0
Net cash used in financing activities	0	0
Effect of exchange rate changes on cash and cash equivalents	0	0
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents—beginning of period	0	0
Cash and cash equivalents—end of period	$ 0	$ 0

Subsequent Events (Details)

Subsequent Events (Details) - Senior secured term loan facility	Apr. 03, 2018	Mar. 31, 2018
Subsequent Event [Line Items]
Net leverage ratio		2.49
Subsequent Event
Subsequent Event [Line Items]
Margin on borrowings, reduced interest rate from refinancing in bps	0.25%
ABR
Subsequent Event [Line Items]
Variable interest rate margin		1.00%
ABR | Subsequent Event
Subsequent Event [Line Items]
Variable interest rate margin	0.75%
LIBOR
Subsequent Event [Line Items]
Margin on borrowings, reduced interest rate from refinancing in bps		0.25%
Variable interest rate margin		2.00%
LIBOR | Subsequent Event
Subsequent Event [Line Items]
Variable interest rate margin	1.75%
Maximum | Subsequent Event
Subsequent Event [Line Items]
Net leverage ratio	3.75