CDW (CDW) 10-Q5 May 212021 Q1 Quarterly reportFinancial data

Company Profile

Cover Page

Cover Page - shares	3 Months Ended
Cover Page - shares	Mar. 31, 2021	Apr. 30, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2021
Entity File Number	001-35985
Entity Central Index Key	0001402057
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Entity Registrant Name	CDW CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-0273989
Entity Address, Address Line One	75 Tri-State International
Entity Address, City or Town	Lincolnshire
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60069
City Area Code	847
Local Phone Number	465-6000
Title of 12(b) Security	Common stock, par value $0.01 per share
Trading Symbol	CDW
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		140,203,541
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 878.6	$ 1,410.2
Accounts receivable, net of allowance for credit losses of $27.0 and $29.6, respectively	3,234.1	3,212.6
Merchandise inventory	745.1	760
Miscellaneous receivables	396.6	379.5
Prepaid expenses and other	215.4	191.2
Total current assets	5,469.8	5,953.5
Operating lease right-of-use assets	128.3	130.8
Property and equipment, net	175.5	175.5
Goodwill	2,812.4	2,595.9
Other intangible assets, net	419.2	445.1
Other assets	48.3	43.9
Total Assets	9,053.5	9,344.7
Current liabilities:
Accounts payable-trade	2,050.8	2,088.4
Accounts payable-inventory financing	344.8	524.6
Current maturities of long-term debt	19.6	70.9
Contract liabilities	326.5	243.7
Accrued expenses and other current liabilities:
Compensation	240.7	288.3
Advertising	166.3	153.4
Sales and income taxes	162.6	104.2
Other	398	424.8
Total current liabilities	3,709.3	3,898.3
Long-term liabilities:
Debt	3,911.1	3,856.3
Deferred income taxes	29.2	55.3
Operating lease liabilities	165.1	169
Other liabilities	68.5	68.7
Total long-term liabilities	4,173.9	4,149.3
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; 140.4 and 141.9 shares outstanding, respectively	1.4	1.4
Paid-in capital	3,262.6	3,204.9
Accumulated deficit	(2,004.6)	(1,813.4)
Accumulated other comprehensive loss	(89.1)	(95.8)
Total stockholders' equity	1,170.3	1,297.1
Total Liabilities and Stockholders' Equity	$ 9,053.5	$ 9,344.7

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for credit loss, current	$ 27	$ 29.6
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	100,000,000	100,000,000
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)	1,000,000,000	1,000,000,000
Common stock, shares outstanding (in shares)	140,400,000	141,900,000

Consolidated Statements Of Oper

Consolidated Statements Of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Net sales	$ 4,837.5	$ 4,389.2
Cost of sales	4,042.3	3,632.7
Gross profit	795.2	756.5
Selling and administrative expenses	471.8	510.7
Operating income	323.4	245.8
Interest expense, net	(35.6)	(37.9)
Other income, net	1.1	3.9
Income before income taxes	288.9	211.8
Income tax expense	(56.3)	(43.9)
Net income	$ 232.6	$ 167.9
Net income per common share:
Basic (in dollars per share)	$ 1.65	$ 1.18
Diluted (in dollars per share)	$ 1.63	$ 1.16
Weighted-average common shares outstanding:
Basic (in shares)	141.1	142.7
Diluted (in shares)	143.1	144.9

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 232.6	$ 167.9
Other comprehensive income (loss):
Unrealized loss from hedge accounting, net of tax	0	(0.2)
Reclassification of hedge accounting loss to net income, net of tax	0.4	1.1
Foreign currency translation, net of tax	6.3	(42.4)
Other comprehensive income (loss)	6.7	(41.5)
Comprehensive income	$ 239.3	$ 126.4

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, AdjustmentAccumulated Deficit
Beginning balance (in shares) at Dec. 31, 2019		143
Beginning balance at Dec. 31, 2019	$ 960.3	$ 1.4	$ 3,095.3	$ (2,018.6)	$ (117.8)	$ 0.5	$ 0.5
Shareholders' Equity (Deficit) [Roll Forward]
Net income	167.9			167.9
Equity-based compensation expense	8.8		8.8
Stock option exercises (in shares)		0.4
Stock option exercises	7.1		7.1
Coworker Stock Purchase Plan	3.5		3.5
Repurchases of common stock (in shares)		(1.1)
Repurchases of common stock	(140.8)	$ 0		(140.8)
Dividends paid	(54.2)		0.2	(54.4)
Incentive compensation plan stock withheld for taxes	(21.9)			(21.9)
Unrealized (loss) gain from hedge accounting	(0.2)				(0.2)
Reclassification of hedge accounting loss to net income	1.1				1.1
Foreign currency translation	(42.4)				(42.4)
Ending balance (in shares) at Mar. 31, 2020		142.3
Ending balance at Mar. 31, 2020	889.7	$ 1.4	3,114.9	(2,067.3)	(159.3)
Beginning balance (in shares) at Dec. 31, 2020		141.9
Beginning balance at Dec. 31, 2020	1,297.1	$ 1.4	3,204.9	(1,813.4)	(95.8)	$ 19.2	$ 19.2
Shareholders' Equity (Deficit) [Roll Forward]
Net income	232.6			232.6
Equity-based compensation expense	15.8		15.8
Stock option exercises (in shares)		0.9
Stock option exercises	37.7		37.7
Coworker Stock Purchase Plan	3.9		3.9
Repurchases of common stock (in shares)		(2.4)
Repurchases of common stock	(358.4)	$ 0		(358.4)
Dividends paid	(56.5)		0.3	(56.8)
Incentive compensation plan stock withheld for taxes	(27.8)			(27.8)
Unrealized (loss) gain from hedge accounting	0
Reclassification of hedge accounting loss to net income	0.4				0.4
Foreign currency translation	6.3				6.3
Ending balance (in shares) at Mar. 31, 2021		140.4
Ending balance at Mar. 31, 2021	$ 1,170.3	$ 1.4	$ 3,262.6	$ (2,004.6)	$ (89.1)

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Stockholders' Equity [Abstract]
Dividends (in dollars per share)	$ 0.40	$ 0.38
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201912Member	us-gaap:AccountingStandardsUpdate201613Member

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net income	$ 232.6	$ 167.9
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	45.2	91.4
Equity-based compensation expense	15.8	8.8
Deferred income taxes	(3.5)	2.6
Provision for credit losses	(1.3)	29.2
Other	2.6	1.4
Changes in assets and liabilities:
Accounts receivable	(15.7)	(209)
Merchandise inventory	15.4	(66.4)
Other assets	(35.8)	(63.7)
Accounts payable-trade	(37.2)	157.4
Other liabilities	126.5	103.4
Net cash provided by operating activities	344.6	223
Cash flows used in investing activities:
Capital expenditures	(20.7)	(25.4)
Acquisition of business, net of cash acquired	(212.9)	0
Net cash used in investing activities	(233.6)	(25.4)
Cash flows used in financing activities:
Proceeds from borrowings under revolving credit facility	56.5	781
Repayments of borrowings under revolving credit facility	0	(619.5)
Payments to extinguish long-term debt	(56.5)	0
Net change in accounts payable-inventory financing	(180.3)	(81.4)
Financing payments for revenue generating assets	(42.9)	0
Repurchases of common stock	(358.4)	(140.8)
Proceeds from stock option exercises	37.7	7.1
Payment of incentive compensation plan withholding taxes	(27.8)	(21.9)
Dividend payments	(56.5)	(54.2)
Other	(15.3)	(0.3)
Net cash used in financing activities	(643.5)	(130)
Effect of exchange rate changes on cash and cash equivalents	0.9	(7.2)
Net (decrease) increase in cash and cash equivalents	(531.6)	60.4
Cash and cash equivalents—beginning of period	1,410.2	154
Cash and cash equivalents—end of period	878.6	214.4
Supplementary disclosure of cash flow information:
Interest paid	(19.2)	(28.6)
Income taxes paid, net	$ (10.1)	$ (9.9)

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
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"), a Fortune 500 company and member of the S&P 500 Index, is a leading multi-brand provider of 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 broad array of offerings ranges from discrete hardware and software products to integrated IT solutions and services that include on-premise, hybrid and cloud capabilities across data center and networking, digital workspace, security and virtualization. Throughout this report, the terms the "Company" and "CDW" refer to Parent and its 100% owned subsidiaries. Parent has two 100% owned subsidiaries, CDW LLC and CDW Finance Corporation. CDW LLC is an Illinois limited liability company that, together with its 100% owned subsidiaries, holds all material assets and conducts all business activities and operations of the Company. CDW Finance Corporation is a Delaware corporation formed for the sole purpose of acting as co-issuer of certain debt obligations and does not hold any material assets or engage in any business activities or operations. Basis of Presentation The accompanying unaudited interim Consolidated Financial Statements as of March 31, 2021 and for the three months ended March 31, 2021 and 2020 (the "Consolidated Financial Statements") have been prepared in conformity with accounting principles generally accepted in the United States of America ("US 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 US 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, 2020 (the "December 31, 2020 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, 2020 Consolidated Financial Statements. In the opinion of management, the Consolidated Financial Statements contain all adjustments (consisting of a normal, recurring nature) necessary to present fairly the Company's financial position, results of operations, comprehensive income, cash flows and changes in stockholders' equity as of the dates and for the periods indicated. The unaudited results of operations for such interim periods reported are not necessarily indicative of results for the full year. Reclassifications Certain prior period amounts have been reclassified to conform with current period presentation. Principles of Consolidation The 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 US GAAP requires management to make 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 and outcomes could differ from those estimates. The notes to the Consolidated Financial Statements contained in the December 31, 2020 Consolidated Financial Statements include a discussion of the Company's significant accounting policies and estimates. Except as noted within Note 2 (Recent Accounting Pronouncements) for the adoption of Accounting Standards Update ("ASU") 2019-12,

Recent Accounting Pronouncement

Recent Accounting Pronouncements	3 Months Ended
Recent Accounting Pronouncements	Mar. 31, 2021
Accounting Standards Update and Change in Accounting Principle [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting for Income Taxes On January 1, 2021, the Company adopted and applied ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes ("Topic 740") in accordance with the applicable transition methods. Among the various updates, the Company adopted the accounting for ownership changes when transitioning from the equity method to consolidation on a modified retrospective basis, which resulted in a $19 million adjustment to retained earnings as of January 1, 2021 for the cumulative effect of derecognizing the deferred tax liability related to the UK acquisition. The adoption of the remaining components of Topic 740 did not have an impact to the Company’s Consolidated Financial Statements. Reference Rate Reform In March 2020, the Financial Accounting Standards Board issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting, followed by an amendment issued in January 2021. This ASU temporarily provides optional expedients and exceptions for applying existing guidance to contract modifications, hedging relationships and other transactions that are expected to be affected by reference rate reform. This ASU, as amended, was effective upon issuance and will remain in effect for all contract modifications and hedging relationships entered into through December 31, 2022. The adoption of this ASU along with the related expedients did not have an impact to the Company’s Consolidated Financial Statements.

Acquisition

Acquisition	3 Months Ended
Acquisition	Mar. 31, 2021
Business Combinations [Abstract]
Acquisition	AcquisitionOn March 15, 2021, the Company completed the acquisition of Amplified IT LLC ("Amplified IT") through a purchase of all issued and outstanding membership interests. Amplified IT is a Google Premium education partner and leading provider of Google Cloud services, solutions and software for education partners. This strategic acquisition expands the Company's services and solutions capabilities to help schools leverage technology to achieve greater educational outcomes. The purchase price allocation will be completed as additional information about fair value of assets and liabilities becomes available.

Goodwill

Goodwill	3 Months Ended
Goodwill	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill The changes in goodwill by reportable segment are as follows: Corporate Small Business Public Other (1) Consolidated Balances as of December 31, 2020 (2) $ 1,123.6 $ 185.9 $ 929.6 $ 356.8 $ 2,595.9 Amplified IT acquisition (3) — — 212.9 — 212.9 Other acquisition adjustments 0.2 — — — 0.2 Foreign currency translation — — — 3.4 3.4 Balances as of March 31, 2021 (2) $ 1,123.8 $ 185.9 $ 1,142.5 $ 360.2 $ 2,812.4 (1) Other is comprised of CDW UK and CDW Canada operating segments. (2) Goodwill is net of accumulated impairment losses of $1,571 million, $354 million and $28 million related to the Corporate, Public and Other segments, respectively. (3) For additional information regarding the Company's acquisition, see Note 3 (Acquisition).

Inventory Financing Agreements

Inventory Financing Agreements	3 Months Ended
Inventory Financing Agreements	Mar. 31, 2021
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: March 31, 2021 December 31, 2020 Revolving Loan inventory financing agreement (1) $ 296.1 $ 470.1 Other inventory financing agreements 48.7 54.5 Accounts payable-inventory financing $ 344.8 $ 524.6 (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 Perfor

Contract Liabilities and Performance Obligations	3 Months Ended
Contract Liabilities and Performance Obligations	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
Contract Liabilities and Performance Obligations	Contract Liabilities and 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, 2021 and December 31, 2020, the contract liability balance was $327 million and $244 million, respectively. During the three months ended March 31, 2021 and 2020, the Company recognized revenue of $97 million and $123 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. The following table represents the total transaction price for the remaining performance obligations as of March 31, 2021 related to noncancelable contracts longer than 12 months in duration that is expected to be recognized over future periods. Within 1 Year Years 1-2 Years 2-3 Thereafter Remaining performance obligations $ 39.5 $ 23.9 $ 9.7 $ 1.5

Long-Term Debt

Long-Term Debt	3 Months Ended
Long-Term Debt	Mar. 31, 2021
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt As of March 31, 2021 As of December 31, 2020 Maturity Date Interest Rate Amount Interest Rate Amount Credit Facility Senior secured asset-based revolving credit facility March 2026 1.375 % $ 56.5 — % $ — Term Loans CDW UK term loan (1) August 2021 — % — 1.445 % 56.0 Senior secured term loan facility October 2026 1.860 % 1,419.6 1.900 % 1,423.4 Total term loans 1,419.6 1,479.4 Unsecured Senior Notes Senior notes due 2024 December 2024 5.500 % 575.0 5.500 % 575.0 Senior notes due 2025 May 2025 4.125 % 600.0 4.125 % 600.0 Senior notes due 2028 April 2028 4.250 % 600.0 4.250 % 600.0 Senior notes due 2029 February 2029 3.250 % 700.0 3.250 % 700.0 Total unsecured senior notes 2,475.0 2,475.0 Other long-term obligations 5.6 — Unamortized deferred financing fees (26.0) (27.2) Current maturities of long-term debt (19.6) (70.9) Total long-term debt $ 3,911.1 $ 3,856.3 (1) Denominated in British pounds. As of March 31, 2021, the Company is in compliance with the covenants under the various credit agreements and indentures. Credit Facility The Company has a variable rate senior secured asset-based revolving credit facility (the "Revolving Loan") that is denominated in US dollars. The Revolving Loan is used by the Company for borrowings, issuances of letters of credit and floorplan financing. As of March 31, 2021, the Revolving Loan had less than $1 million of undrawn letters of credit, $283 million reserved for the floorplan sub-facility and a borrowing base of $2.2 billion, which is based on the amount of eligible inventory and accounts receivable balances as of February 28, 2021. As of March 31, 2021, the Company could have borrowed up to an additional $1.3 billion under the Revolving Loan. The Revolving Loan is collateralized by a first priority interest in inventory (excluding inventory to the extent collateralized under the inventory financing arrangements as described in Note 5 (Inventory Financing Agreements)), deposits and accounts receivable, and by a second priority interest in substantially all other US assets. Term Loan The senior secured term loan facility (the "Term Loan") has a variable interest rate, which has effectively been capped through the use of interest rate caps. The interest rates disclosed in the table above represent the variable interest rates in effect for March 31, 2021 and December 31, 2020, respectively. The Company is required to pay quarterly principal installments of $4 million with the remaining principal amount due at the maturity date. As of March 31, 2021, the amount of CDW's restricted payment capacity under the Term Loan was $2.4 billion. The Term Loan is collateralized by a second priority interest in substantially all inventory (excluding inventory to the extent collateralized under the inventory financing arrangements as described in Note 5 (Inventory Financing Agreements), deposits and accounts receivable, and by a first priority interest in substantially all other US assets. Unsecured Senior Notes The Senior Notes have fixed interest rates, for which interest is paid semi-annually. Issuances and Extinguishments During the first quarter of 2021, the Company amended, extended and increased the size of the Revolving Loan. The amended Revolving Loan (i) authorized CDW UK to draw from the facility, (ii) increased the capacity from $1.45 billion to $1.60 billion, of which $150 million may be borrowed by CDW UK, and (iii) extended the maturity date from March 31, 2022 to March 26, 2026. Due to the addition of CDW UK as a borrower on the amended Revolving Loan, the variable rate CDW UK revolving credit facility was closed. The Company may borrow amounts denominated in US dollars, British pounds or Euros. Additionally, the Company paid off the remaining principal amount on the variable rate CDW UK term loan by drawing on the amended Revolving Loan. 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 and Term Loan were classified as Level 2 within the fair value hierarchy. The carrying value of the Revolving Loan approximates its fair value if there are outstanding borrowings. 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: March 31, 2021 December 31, 2020 Fair value $ 4,029.9 $ 4,077.9 Carrying value 3,956.7 3,954.4

Income Taxes

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income TaxesIncome tax expense was $56 million and $44 million for the three months ended March 31, 2021 and 2020, respectively. The effective tax rate, expressed by calculating the income tax expense as a percentage of Income before income taxes, was 19.5% and 20.7% for the three months ended March 31, 2021 and 2020, respectively. The effective income tax rate for the three months ended March 31, 2021 and 2020 differed from the US federal statutory rate of 21.0% primarily due to excess tax benefits on equity-based compensation, partially offset by state and local income taxes.

Earnings per Share

Earnings per Share	3 Months Ended
Earnings per Share	Mar. 31, 2021
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, 2021 2020 Basic weighted-average shares outstanding 141.1 142.7 Effect of dilutive securities (1) 2.0 2.2 Diluted weighted-average shares outstanding (2) 143.1 144.9 (1) The dilutive effect of outstanding stock options, restricted stock units, 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 fewer than 0.1 million potential common shares excluded from diluted weighted-average shares outstanding for both the three months ended March 31, 2021 and 2020 as their inclusion would have had an anti-dilutive effect.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2021
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, 2021, 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 consolidated financial statements 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
Segment Information	Mar. 31, 2021
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, which primarily serves 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"). Headquarters function costs that are not allocated to the segments are included under the heading of "Headquarters" in the tables below. Information about the Company's segments is as follows: Corporate Small Business Public Other Headquarters Total Three Months Ended March 31, 2021 Net sales $ 1,805.6 $ 432.7 $ 1,921.7 $ 677.5 $ — $ 4,837.5 Operating income (loss) 161.4 42.8 136.7 27.7 (45.2) 323.4 Depreciation and amortization expense (4.0) (0.8) (13.4) (8.6) (18.4) (45.2) Three Months Ended March 31, 2020 Net sales $ 1,911.0 $ 391.5 $ 1,525.3 $ 561.4 $ — $ 4,389.2 Operating income (loss) 127.4 27.3 112.4 14.7 (36.0) 245.8 Depreciation and amortization expense (22.3) (5.8) (37.7) (8.0) (17.6) (91.4) Geographic Areas and Revenue Mix Three Months Ended March 31, 2021 Corporate Small Business Public Other Total Geography (1) United States $ 1,803.5 $ 432.7 $ 1,921.7 $ 4.6 $ 4,162.5 Rest of World 2.1 — — 672.9 675.0 Total Net sales 1,805.6 432.7 1,921.7 677.5 4,837.5 Major Product and Services Hardware 1,420.6 368.1 1,664.9 511.6 3,965.2 Software 267.3 49.2 194.4 99.1 610.0 Services 102.5 10.1 57.9 63.2 233.7 Other (2) 15.2 5.3 4.5 3.6 28.6 Total Net sales 1,805.6 432.7 1,921.7 677.5 4,837.5 Sales by Channel Corporate 1,805.6 — — — 1,805.6 Small Business — 432.7 — — 432.7 Government — — 516.1 — 516.1 Education — — 943.3 — 943.3 Healthcare — — 462.3 — 462.3 Other — — — 677.5 677.5 Total Net sales 1,805.6 432.7 1,921.7 677.5 4,837.5 Timing of Revenue Recognition Transferred at a point in time where CDW is principal 1,627.7 402.0 1,825.9 600.6 4,456.2 Transferred at a point in time where CDW is agent 112.3 26.9 58.1 23.4 220.7 Transferred over time where CDW is principal 65.6 3.8 37.7 53.5 160.6 Total Net sales $ 1,805.6 $ 432.7 $ 1,921.7 $ 677.5 $ 4,837.5 (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, 2020 Corporate Small Business Public Other Total Geography (1) United States $ 1,907.8 $ 391.5 $ 1,525.3 $ 6.2 $ 3,830.8 Rest of World 3.2 — — 555.2 558.4 Total Net sales 1,911.0 391.5 1,525.3 561.4 4,389.2 Major Product and Services (2) Hardware 1,517.7 325.1 1,214.9 411.4 3,469.1 Software 272.3 52.8 235.4 93.2 653.7 Services 100.0 8.2 67.8 54.5 230.5 Other (3) 21.0 5.4 7.2 2.3 35.9 Total Net sales 1,911.0 391.5 1,525.3 561.4 4,389.2 Sales by Channel Corporate 1,911.0 — — — 1,911.0 Small Business — 391.5 — — 391.5 Government — — 568.5 — 568.5 Education — — 476.2 — 476.2 Healthcare — — 480.6 — 480.6 Other — — — 561.4 561.4 Total Net sales 1,911.0 391.5 1,525.3 561.4 4,389.2 Timing of Revenue Recognition Transferred at a point in time where CDW is principal 1,741.0 366.7 1,404.6 499.0 4,011.3 Transferred at a point in time where CDW is agent 107.6 22.0 52.3 13.2 195.1 Transferred over time where CDW is principal 62.4 2.8 68.4 49.2 182.8 Total Net sales $ 1,911.0 $ 391.5 $ 1,525.3 $ 561.4 $ 4,389.2 (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) Amounts have been reclassified for changes in individual product classifications to conform to the presentation for the three months ended March 31, 2021. (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, 2021 and 2020. Categories are based upon internal classifications. Three Months Ended March 31, 2021 2020 (1) Net Sales Percentage Net Sales Percentage Notebooks/Mobile Devices $ 1,591.8 32.9 % $ 1,110.5 25.3 % Netcomm Products 454.7 9.4 455.2 10.4 Desktops 265.3 5.5 382.3 8.7 Video 326.2 6.7 313.6 7.1 Enterprise and Data Storage (Including Drives) 259.9 5.4 240.9 5.5 Other Hardware 1,067.3 22.1 966.6 22.0 Total Hardware 3,965.2 82.0 3,469.1 79.0 Software (2) 610.0 12.6 653.7 14.9 Services (2) 233.7 4.8 230.5 5.3 Other (3) 28.6 0.6 35.9 0.8 Total Net sales $ 4,837.5 100.0 % $ 4,389.2 100.0 % (1) Amounts have been reclassified for changes in individual product classifications to conform to the presentation for the three months ended March 31, 2021. (2) Certain software and services revenues are recorded on a net basis as the Company is acting as an agent in the transaction. 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.

Description of Business and S_2

Description of Business and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Description of Business	Description of Business CDW Corporation ("Parent"), a Fortune 500 company and member of the S&P 500 Index, is a leading multi-brand provider of 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 broad array of offerings ranges from discrete hardware and software products to integrated IT solutions and services that include on-premise, hybrid and cloud capabilities across data center and networking, digital workspace, security and virtualization. Throughout this report, the terms the "Company" and "CDW" refer to Parent and its 100% owned subsidiaries. Parent has two 100% owned subsidiaries, CDW LLC and CDW Finance Corporation. CDW LLC is an Illinois limited liability company that, together with its 100% owned subsidiaries, holds all material assets and conducts all business activities and operations of the Company. CDW Finance Corporation is a Delaware corporation formed for the sole purpose of acting as co-issuer of certain debt obligations and does not hold any material assets or engage in any business activities or operations.
Basis of Presentation	Basis of Presentation The accompanying unaudited interim Consolidated Financial Statements as of March 31, 2021 and for the three months ended March 31, 2021 and 2020 (the "Consolidated Financial Statements") have been prepared in conformity with accounting principles generally accepted in the United States of America ("US 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 US 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, 2020 (the "December 31, 2020 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, 2020 Consolidated Financial Statements. In the opinion of management, the Consolidated Financial Statements contain all adjustments (consisting of a normal, recurring nature) necessary to present fairly the Company's financial position, results of operations, comprehensive income, cash flows and changes in stockholders' equity as of the dates and for the periods indicated. The unaudited results of operations for such interim periods reported are not necessarily indicative of results for the full year.
Reclassification	Reclassifications Certain prior period amounts have been reclassified to conform with current period presentation.
Principles of Consolidation	Principles of Consolidation The 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 US GAAP requires management to make 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 and outcomes could differ from those estimates.
Recent Accounting Pronouncements	Reference Rate Reform In March 2020, the Financial Accounting Standards Board issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting, followed by an amendment issued in January 2021. This ASU temporarily provides optional expedients and exceptions for applying existing guidance to contract modifications, hedging relationships and other transactions that are expected to be affected by reference rate reform. This ASU, as amended, was effective upon issuance and will remain in effect for all contract modifications and hedging relationships entered into through December 31, 2022. The adoption of this ASU along with the related expedients did not have an impact to the Company’s Consolidated Financial Statements.

Goodwill (Tables)

Goodwill (Tables)	3 Months Ended
Goodwill (Tables)	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The changes in goodwill by reportable segment are as follows: Corporate Small Business Public Other (1) Consolidated Balances as of December 31, 2020 (2) $ 1,123.6 $ 185.9 $ 929.6 $ 356.8 $ 2,595.9 Amplified IT acquisition (3) — — 212.9 — 212.9 Other acquisition adjustments 0.2 — — — 0.2 Foreign currency translation — — — 3.4 3.4 Balances as of March 31, 2021 (2) $ 1,123.8 $ 185.9 $ 1,142.5 $ 360.2 $ 2,812.4 (1) Other is comprised of CDW UK and CDW Canada operating segments. (2) Goodwill is net of accumulated impairment losses of $1,571 million, $354 million and $28 million related to the Corporate, Public and Other segments, respectively. (3) For additional information regarding the Company's acquisition, see Note 3 (Acquisition).

Inventory Financing Agreements

Inventory Financing Agreements (Tables)	3 Months Ended
Inventory Financing Agreements (Tables)	Mar. 31, 2021
Inventory Financing Agreements [Abstract]
Inventory Financing Agreements	Amounts included in Accounts payable-inventory financing are as follows: March 31, 2021 December 31, 2020 Revolving Loan inventory financing agreement (1) $ 296.1 $ 470.1 Other inventory financing agreements 48.7 54.5 Accounts payable-inventory financing $ 344.8 $ 524.6 (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 Perf_2

Contract Liabilities and Performance Obligations (Tables)	3 Months Ended
Contract Liabilities and Performance Obligations (Tables)	Mar. 31, 2021
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, 2021 related to noncancelable contracts longer than 12 months in duration that is expected to be recognized over future periods. Within 1 Year Years 1-2 Years 2-3 Thereafter Remaining performance obligations $ 39.5 $ 23.9 $ 9.7 $ 1.5

Long-Term Debt (Tables)

Long-Term Debt (Tables)	3 Months Ended
Long-Term Debt (Tables)	Mar. 31, 2021
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	As of March 31, 2021 As of December 31, 2020 Maturity Date Interest Rate Amount Interest Rate Amount Credit Facility Senior secured asset-based revolving credit facility March 2026 1.375 % $ 56.5 — % $ — Term Loans CDW UK term loan (1) August 2021 — % — 1.445 % 56.0 Senior secured term loan facility October 2026 1.860 % 1,419.6 1.900 % 1,423.4 Total term loans 1,419.6 1,479.4 Unsecured Senior Notes Senior notes due 2024 December 2024 5.500 % 575.0 5.500 % 575.0 Senior notes due 2025 May 2025 4.125 % 600.0 4.125 % 600.0 Senior notes due 2028 April 2028 4.250 % 600.0 4.250 % 600.0 Senior notes due 2029 February 2029 3.250 % 700.0 3.250 % 700.0 Total unsecured senior notes 2,475.0 2,475.0 Other long-term obligations 5.6 — Unamortized deferred financing fees (26.0) (27.2) Current maturities of long-term debt (19.6) (70.9) Total long-term debt $ 3,911.1 $ 3,856.3
Carrying Value of Long-Term Debt	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: March 31, 2021 December 31, 2020 Fair value $ 4,029.9 $ 4,077.9 Carrying value 3,956.7 3,954.4

Earnings per Share (Tables)

Earnings per Share (Tables)	3 Months Ended
Earnings per Share (Tables)	Mar. 31, 2021
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, 2021 2020 Basic weighted-average shares outstanding 141.1 142.7 Effect of dilutive securities (1) 2.0 2.2 Diluted weighted-average shares outstanding (2) 143.1 144.9 (1) The dilutive effect of outstanding stock options, restricted stock units, 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 fewer than 0.1 million potential common shares excluded from diluted weighted-average shares outstanding for both the three months ended March 31, 2021 and 2020 as their inclusion would have had an anti-dilutive effect.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
Segment Information (Tables)	Mar. 31, 2021
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Information about the Company's segments is as follows: Corporate Small Business Public Other Headquarters Total Three Months Ended March 31, 2021 Net sales $ 1,805.6 $ 432.7 $ 1,921.7 $ 677.5 $ — $ 4,837.5 Operating income (loss) 161.4 42.8 136.7 27.7 (45.2) 323.4 Depreciation and amortization expense (4.0) (0.8) (13.4) (8.6) (18.4) (45.2) Three Months Ended March 31, 2020 Net sales $ 1,911.0 $ 391.5 $ 1,525.3 $ 561.4 $ — $ 4,389.2 Operating income (loss) 127.4 27.3 112.4 14.7 (36.0) 245.8 Depreciation and amortization expense (22.3) (5.8) (37.7) (8.0) (17.6) (91.4)
Disaggregation of Revenue	Geographic Areas and Revenue Mix Three Months Ended March 31, 2021 Corporate Small Business Public Other Total Geography (1) United States $ 1,803.5 $ 432.7 $ 1,921.7 $ 4.6 $ 4,162.5 Rest of World 2.1 — — 672.9 675.0 Total Net sales 1,805.6 432.7 1,921.7 677.5 4,837.5 Major Product and Services Hardware 1,420.6 368.1 1,664.9 511.6 3,965.2 Software 267.3 49.2 194.4 99.1 610.0 Services 102.5 10.1 57.9 63.2 233.7 Other (2) 15.2 5.3 4.5 3.6 28.6 Total Net sales 1,805.6 432.7 1,921.7 677.5 4,837.5 Sales by Channel Corporate 1,805.6 — — — 1,805.6 Small Business — 432.7 — — 432.7 Government — — 516.1 — 516.1 Education — — 943.3 — 943.3 Healthcare — — 462.3 — 462.3 Other — — — 677.5 677.5 Total Net sales 1,805.6 432.7 1,921.7 677.5 4,837.5 Timing of Revenue Recognition Transferred at a point in time where CDW is principal 1,627.7 402.0 1,825.9 600.6 4,456.2 Transferred at a point in time where CDW is agent 112.3 26.9 58.1 23.4 220.7 Transferred over time where CDW is principal 65.6 3.8 37.7 53.5 160.6 Total Net sales $ 1,805.6 $ 432.7 $ 1,921.7 $ 677.5 $ 4,837.5 (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, 2020 Corporate Small Business Public Other Total Geography (1) United States $ 1,907.8 $ 391.5 $ 1,525.3 $ 6.2 $ 3,830.8 Rest of World 3.2 — — 555.2 558.4 Total Net sales 1,911.0 391.5 1,525.3 561.4 4,389.2 Major Product and Services (2) Hardware 1,517.7 325.1 1,214.9 411.4 3,469.1 Software 272.3 52.8 235.4 93.2 653.7 Services 100.0 8.2 67.8 54.5 230.5 Other (3) 21.0 5.4 7.2 2.3 35.9 Total Net sales 1,911.0 391.5 1,525.3 561.4 4,389.2 Sales by Channel Corporate 1,911.0 — — — 1,911.0 Small Business — 391.5 — — 391.5 Government — — 568.5 — 568.5 Education — — 476.2 — 476.2 Healthcare — — 480.6 — 480.6 Other — — — 561.4 561.4 Total Net sales 1,911.0 391.5 1,525.3 561.4 4,389.2 Timing of Revenue Recognition Transferred at a point in time where CDW is principal 1,741.0 366.7 1,404.6 499.0 4,011.3 Transferred at a point in time where CDW is agent 107.6 22.0 52.3 13.2 195.1 Transferred over time where CDW is principal 62.4 2.8 68.4 49.2 182.8 Total Net sales $ 1,911.0 $ 391.5 $ 1,525.3 $ 561.4 $ 4,389.2 (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) Amounts have been reclassified for changes in individual product classifications to conform to the presentation for the three months ended March 31, 2021. (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, 2021 and 2020. Categories are based upon internal classifications. Three Months Ended March 31, 2021 2020 (1) Net Sales Percentage Net Sales Percentage Notebooks/Mobile Devices $ 1,591.8 32.9 % $ 1,110.5 25.3 % Netcomm Products 454.7 9.4 455.2 10.4 Desktops 265.3 5.5 382.3 8.7 Video 326.2 6.7 313.6 7.1 Enterprise and Data Storage (Including Drives) 259.9 5.4 240.9 5.5 Other Hardware 1,067.3 22.1 966.6 22.0 Total Hardware 3,965.2 82.0 3,469.1 79.0 Software (2) 610.0 12.6 653.7 14.9 Services (2) 233.7 4.8 230.5 5.3 Other (3) 28.6 0.6 35.9 0.8 Total Net sales $ 4,837.5 100.0 % $ 4,389.2 100.0 % (1) Amounts have been reclassified for changes in individual product classifications to conform to the presentation for the three months ended March 31, 2021. (2) Certain software and services revenues are recorded on a net basis as the Company is acting as an agent in the transaction. 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.

Description of Business and S_3

Description of Business and Summary of Significant Accounting Policies (Details)	Mar. 31, 2021subsidiary
Accounting Policies [Abstract]
Number of owned subsidiaries	2

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to stockholders' equity attributable to parent	$ 1,170.3	$ 1,297.1	$ 889.7	$ 960.3
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to stockholders' equity attributable to parent	$ (2,004.6)	(1,813.4)	$ (2,067.3)	(2,018.6)
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to stockholders' equity attributable to parent		19.2		0.5
Cumulative Effect, Period of Adoption, Adjustment \| Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to stockholders' equity attributable to parent		$ 19.2		$ 0.5

Goodwill - Schedule of Goodwill

Goodwill - Schedule of Goodwill by Segment (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 2,595.9
Foreign currency translation	3.4
Ending balance	2,812.4
Corporate
Goodwill [Roll Forward]
Beginning balance	1,123.6
Foreign currency translation	0
Ending balance	1,123.8
Accumulated impairment losses	1,571
Small Business
Goodwill [Roll Forward]
Beginning balance	185.9
Foreign currency translation	0
Ending balance	185.9
Public
Goodwill [Roll Forward]
Beginning balance	929.6
Foreign currency translation	0
Ending balance	1,142.5
Accumulated impairment losses	354
Other
Goodwill [Roll Forward]
Beginning balance	356.8
Foreign currency translation	3.4
Ending balance	360.2
Accumulated impairment losses	28
Amplified IT
Goodwill [Roll Forward]
Acquisition	212.9
Amplified IT \| Corporate
Goodwill [Roll Forward]
Acquisition	0
Amplified IT \| Small Business
Goodwill [Roll Forward]
Acquisition	0
Amplified IT \| Public
Goodwill [Roll Forward]
Acquisition	212.9
Amplified IT \| Other
Goodwill [Roll Forward]
Acquisition	0
Other Acquisition
Goodwill [Roll Forward]
Acquisition	0.2
Other Acquisition \| Corporate
Goodwill [Roll Forward]
Acquisition	0.2
Other Acquisition \| Small Business
Goodwill [Roll Forward]
Acquisition	0
Other Acquisition \| Public
Goodwill [Roll Forward]
Acquisition	0
Other Acquisition \| Other
Goodwill [Roll Forward]
Acquisition	$ 0

Inventory Financing Agreement_2

Inventory Financing Agreements (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Inventory Financing Agreements [Line Items]
Accounts payable-inventory financing	$ 344.8	$ 524.6
Accounts Payable, Inventory Financing
Inventory Financing Agreements [Line Items]
Revolving Loan inventory financing agreement	296.1	470.1
Other inventory financing agreements	$ 48.7	$ 54.5

Contract Liabilities and Perf_3

Contract Liabilities and Performance Obligations - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract liabilities	$ 327		$ 244
Revenue recognized from contract with customer	$ 97	$ 123

Contract Liabilities and Perf_4

Contract Liabilities and Performance Obligations - Schedule of Remaining Performance Obligations (Details) $ in Millions	Mar. 31, 2021USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligations	$ 39.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-04-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligations	$ 23.9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-04-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligations	$ 9.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-04-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligations	$ 1.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, expected timing of satisfaction, period

Long-Term Debt - Debt Balances

Long-Term Debt - Debt Balances and Interest Rates (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term debt	$ 3,956.7	$ 3,954.4
Unamortized deferred financing fees	(26)	(27.2)
Current maturities of long-term debt	(19.6)	(70.9)
Total long-term debt	$ 3,911.1	$ 3,856.3
Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Interest rate in effect	1.375%	0.00%
Long-term debt	$ 56.5	$ 0
Total term loans
Debt Instrument [Line Items]
Long-term debt	$ 1,419.6	$ 1,479.4
CDW UK term loan
Debt Instrument [Line Items]
Interest rate in effect	0.00%	1.445%
Long-term debt	$ 0	$ 56
Senior secured term loan facility
Debt Instrument [Line Items]
Interest rate in effect	1.86%	1.90%
Long-term debt	$ 1,419.6	$ 1,423.4
Total unsecured senior notes
Debt Instrument [Line Items]
Long-term debt	$ 2,475	$ 2,475
Senior notes due 2024
Debt Instrument [Line Items]
Interest rate in effect	5.50%	5.50%
Long-term debt	$ 575	$ 575
Senior notes due 2025
Debt Instrument [Line Items]
Interest rate in effect	4.125%	4.125%
Long-term debt	$ 600	$ 600
Senior notes due 2028
Debt Instrument [Line Items]
Interest rate in effect	4.25%	4.25%
Long-term debt	$ 600	$ 600
Senior Notes due 2029
Debt Instrument [Line Items]
Interest rate in effect	3.25%	3.25%
Long-term debt	$ 700	$ 700
Other long-term obligations
Debt Instrument [Line Items]
Long-term debt	$ 5.6	$ 0

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 26, 2021	Mar. 25, 2021
CDW UK revolving credit facility
Debt Instrument [Line Items]
Borrowing capacity of the Revolving Loan	$ 150
Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Undrawn letters of credit	1
Borrowing base	2,200
Additional borrowing capacity	1,300
Senior secured term loan facility
Debt Instrument [Line Items]
Periodic payment, principal	4
Amount of restricted payment capacity under the loan	2,400
Revolving Loan
Debt Instrument [Line Items]
Borrowing capacity of the Revolving Loan		$ 1,600	$ 1,450
Accounts Payable, Inventory Financing \| Senior secured asset-based revolving credit facility
Debt Instrument [Line Items]
Amount owed under Revolving loan financing agreement	$ 283

Long-Term Debt - Fair Value of

Long-Term Debt - Fair Value of Long-Term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value	$ 3,956.7	$ 3,954.4
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value	$ 4,029.9	$ 4,077.9

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income tax (expense) benefit	$ (56.3)	$ (43.9)
Effective income tax rate reconciliation, percent	19.50%	20.70%
Effective income tax rate reconciliation at federal statutory income tax rate, percent	21.00%

Earnings per Share (Details)

Earnings per Share (Details) - shares shares in Millions	3 Months Ended
Earnings per Share (Details) - shares shares in Millions	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Basic weighted-average shares outstanding (in shares)	141.1	142.7
Effect of dilutive securities (in shares)	2	2.2
Diluted weighted-average shares outstanding (in shares)	143.1	144.9
Anti-dilutive shares (fewer than) (in shares)	0.1	0.1

Segment Information - Narrative

Segment Information - Narrative (Details)	3 Months Ended
Segment Information - Narrative (Details)	Mar. 31, 2021segmentemployee
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, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Net sales	$ 4,837.5	$ 4,389.2
Income (loss) from operations	323.4	245.8
Depreciation and amortization expense	(45.2)	(91.4)
Corporate
Segment Reporting Information [Line Items]
Net sales	1,805.6	1,911
Small Business
Segment Reporting Information [Line Items]
Net sales	432.7	391.5
Public
Segment Reporting Information [Line Items]
Net sales	1,921.7	1,525.3
Other
Segment Reporting Information [Line Items]
Net sales	677.5	561.4
Operating Segments \| Corporate
Segment Reporting Information [Line Items]
Net sales	1,805.6	1,911
Income (loss) from operations	161.4	127.4
Depreciation and amortization expense	(4)	(22.3)
Operating Segments \| Small Business
Segment Reporting Information [Line Items]
Net sales	432.7	391.5
Income (loss) from operations	42.8	27.3
Depreciation and amortization expense	(0.8)	(5.8)
Operating Segments \| Public
Segment Reporting Information [Line Items]
Net sales	1,921.7	1,525.3
Income (loss) from operations	136.7	112.4
Depreciation and amortization expense	(13.4)	(37.7)
Operating Segments \| Other
Segment Reporting Information [Line Items]
Net sales	677.5	561.4
Income (loss) from operations	27.7	14.7
Depreciation and amortization expense	(8.6)	(8)
Headquarters
Segment Reporting Information [Line Items]
Net sales	0	0
Income (loss) from operations	(45.2)	(36)
Depreciation and amortization expense	$ (18.4)	$ (17.6)

Segment Information - Disaggreg

Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Net sales	$ 4,837.5	$ 4,389.2
Percentage of Total Net Sales	100.00%	100.00%
Corporate
Disaggregation of Revenue [Line Items]
Net sales	$ 1,805.6	$ 1,911
Small Business
Disaggregation of Revenue [Line Items]
Net sales	432.7	391.5
Public
Disaggregation of Revenue [Line Items]
Net sales	1,921.7	1,525.3
Other
Disaggregation of Revenue [Line Items]
Net sales	677.5	561.4
Transferred at a point in time where CDW is principal
Disaggregation of Revenue [Line Items]
Net sales	4,456.2	4,011.3
Transferred at a point in time where CDW is principal \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	1,627.7	1,741
Transferred at a point in time where CDW is principal \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	402	366.7
Transferred at a point in time where CDW is principal \| Public
Disaggregation of Revenue [Line Items]
Net sales	1,825.9	1,404.6
Transferred at a point in time where CDW is principal \| Other
Disaggregation of Revenue [Line Items]
Net sales	600.6	499
Transferred at a point in time where CDW is agent
Disaggregation of Revenue [Line Items]
Net sales	220.7	195.1
Transferred at a point in time where CDW is agent \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	112.3	107.6
Transferred at a point in time where CDW is agent \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	26.9	22
Transferred at a point in time where CDW is agent \| Public
Disaggregation of Revenue [Line Items]
Net sales	58.1	52.3
Transferred at a point in time where CDW is agent \| Other
Disaggregation of Revenue [Line Items]
Net sales	23.4	13.2
Transferred over time where CDW is principal
Disaggregation of Revenue [Line Items]
Net sales	160.6	182.8
Transferred over time where CDW is principal \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	65.6	62.4
Transferred over time where CDW is principal \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	3.8	2.8
Transferred over time where CDW is principal \| Public
Disaggregation of Revenue [Line Items]
Net sales	37.7	68.4
Transferred over time where CDW is principal \| Other
Disaggregation of Revenue [Line Items]
Net sales	53.5	49.2
Corporate
Disaggregation of Revenue [Line Items]
Net sales	1,805.6	1,911
Corporate \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	1,805.6	1,911
Corporate \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Corporate \| Public
Disaggregation of Revenue [Line Items]
Net sales	0	0
Corporate \| Other
Disaggregation of Revenue [Line Items]
Net sales	0	0
Small Business
Disaggregation of Revenue [Line Items]
Net sales	432.7	391.5
Small Business \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	0	0
Small Business \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	432.7	391.5
Small Business \| Public
Disaggregation of Revenue [Line Items]
Net sales	0	0
Small Business \| Other
Disaggregation of Revenue [Line Items]
Net sales	0	0
Government
Disaggregation of Revenue [Line Items]
Net sales	516.1	568.5
Government \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	0	0
Government \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Government \| Public
Disaggregation of Revenue [Line Items]
Net sales	516.1	568.5
Government \| Other
Disaggregation of Revenue [Line Items]
Net sales	0	0
Education
Disaggregation of Revenue [Line Items]
Net sales	943.3	476.2
Education \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	0	0
Education \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Education \| Public
Disaggregation of Revenue [Line Items]
Net sales	943.3	476.2
Education \| Other
Disaggregation of Revenue [Line Items]
Net sales	0	0
Healthcare
Disaggregation of Revenue [Line Items]
Net sales	462.3	480.6
Healthcare \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	0	0
Healthcare \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Healthcare \| Public
Disaggregation of Revenue [Line Items]
Net sales	462.3	480.6
Healthcare \| Other
Disaggregation of Revenue [Line Items]
Net sales	0	0
Other
Disaggregation of Revenue [Line Items]
Net sales	677.5	561.4
Other \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	0	0
Other \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Other \| Public
Disaggregation of Revenue [Line Items]
Net sales	0	0
Other \| Other
Disaggregation of Revenue [Line Items]
Net sales	677.5	561.4
Hardware
Disaggregation of Revenue [Line Items]
Net sales	$ 3,965.2	$ 3,469.1
Percentage of Total Net Sales	82.00%	79.00%
Hardware \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	$ 1,420.6	$ 1,517.7
Hardware \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	368.1	325.1
Hardware \| Public
Disaggregation of Revenue [Line Items]
Net sales	1,664.9	1,214.9
Hardware \| Other
Disaggregation of Revenue [Line Items]
Net sales	511.6	411.4
Notebooks/Mobile Devices
Disaggregation of Revenue [Line Items]
Net sales	$ 1,591.8	$ 1,110.5
Percentage of Total Net Sales	32.90%	25.30%
Netcomm Products
Disaggregation of Revenue [Line Items]
Net sales	$ 454.7	$ 455.2
Percentage of Total Net Sales	9.40%	10.40%
Desktops
Disaggregation of Revenue [Line Items]
Net sales	$ 265.3	$ 382.3
Percentage of Total Net Sales	5.50%	8.70%
Video
Disaggregation of Revenue [Line Items]
Net sales	$ 326.2	$ 313.6
Percentage of Total Net Sales	6.70%	7.10%
Enterprise and Data Storage (Including Drives)
Disaggregation of Revenue [Line Items]
Net sales	$ 259.9	$ 240.9
Percentage of Total Net Sales	5.40%	5.50%
Other Hardware
Disaggregation of Revenue [Line Items]
Net sales	$ 1,067.3	$ 966.6
Percentage of Total Net Sales	22.10%	22.00%
Software
Disaggregation of Revenue [Line Items]
Net sales	$ 610	$ 653.7
Percentage of Total Net Sales	12.60%	14.90%
Software \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	$ 267.3	$ 272.3
Software \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	49.2	52.8
Software \| Public
Disaggregation of Revenue [Line Items]
Net sales	194.4	235.4
Software \| Other
Disaggregation of Revenue [Line Items]
Net sales	99.1	93.2
Services
Disaggregation of Revenue [Line Items]
Net sales	$ 233.7	$ 230.5
Percentage of Total Net Sales	4.80%	5.30%
Services \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	$ 102.5	$ 100
Services \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	10.1	8.2
Services \| Public
Disaggregation of Revenue [Line Items]
Net sales	57.9	67.8
Services \| Other
Disaggregation of Revenue [Line Items]
Net sales	63.2	54.5
Other
Disaggregation of Revenue [Line Items]
Net sales	$ 28.6	$ 35.9
Percentage of Total Net Sales	0.60%	0.80%
Other \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	$ 15.2	$ 21
Other \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	5.3	5.4
Other \| Public
Disaggregation of Revenue [Line Items]
Net sales	4.5	7.2
Other \| Other
Disaggregation of Revenue [Line Items]
Net sales	3.6	2.3
United States
Disaggregation of Revenue [Line Items]
Net sales	4,162.5	3,830.8
United States \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	1,803.5	1,907.8
United States \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	432.7	391.5
United States \| Public
Disaggregation of Revenue [Line Items]
Net sales	1,921.7	1,525.3
United States \| Other
Disaggregation of Revenue [Line Items]
Net sales	4.6	6.2
Rest of World
Disaggregation of Revenue [Line Items]
Net sales	675	558.4
Rest of World \| Corporate
Disaggregation of Revenue [Line Items]
Net sales	2.1	3.2
Rest of World \| Small Business
Disaggregation of Revenue [Line Items]
Net sales	0	0
Rest of World \| Public
Disaggregation of Revenue [Line Items]
Net sales	0	0
Rest of World \| Other
Disaggregation of Revenue [Line Items]
Net sales	$ 672.9	$ 555.2