Segment Information (Tables)

3 Months Ended

Mar. 31, 2020

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, 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		)
Three Months Ended March 31, 2019
Net sales	$	1,736.2		$	355.6		$	1,330.7		$	535.4		$	—		$	3,957.9
Operating income (loss)	134.7			24.4			76.1			25.6			(31.9		)	228.9
Depreciation and amortization expense	(21.5		)	(5.6		)	(12.7		)	(7.4		)	(17.1		)	(64.3		)

Disaggregation of Revenue

Geographic Areas and Revenue Mix

	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
Hardware	1,513.9		324.4		1,210.8		407.4		3,456.5
Software	276.0		53.5		239.7		97.1		666.3
Services	100.1		8.2		67.8		54.5		230.6
Other(2)	21.0		5.4		7.0		2.4		35.8
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) Includes items such as delivery charges to customers.

	Three Months Ended March 31, 2019
	Corporate		Small Business		Public		Other		Total
Geography(1)
United States	$	1,732.9	$	355.6	$	1,330.7	$	8.4	$	3,427.6
Rest of World	3.3		—		—		527.0		530.3
Total Net sales	1,736.2		355.6		1,330.7		535.4		3,957.9
Major Product and Services
Hardware	1,384.7		295.1		1,063.3		403.2		3,146.3
Software	246.5		48.1		221.1		77.3		593.0
Services	88.0		7.0		42.1		51.9		189.0
Other(2)	17.0		5.4		4.2		3.0		29.6
Total Net sales	1,736.2		355.6		1,330.7		535.4		3,957.9
Sales by Channel
Corporate	1,736.2		—		—		—		1,736.2
Small Business	—		355.6		—		—		355.6
Government	—		—		488.4		—		488.4
Education	—		—		400.4		—		400.4
Healthcare	—		—		441.9		—		441.9
Other	—		—		—		535.4		535.4
Total Net sales	1,736.2		355.6		1,330.7		535.4		3,957.9
Timing of Revenue Recognition
Transferred at a point in time where CDW is principal	1,581.8		335.2		1,243.3		474.9		3,635.2
Transferred at a point in time where CDW is agent	104.0		19.8		46.2		13.0		183.0
Transferred over time where CDW is principal	50.4		0.6		41.2		47.5		139.7
Total Net sales	$	1,736.2	$	355.6	$	1,330.7	$	535.4	$	3,957.9

(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.

The following table presents Net sales by major category for the three months ended March 31, 2020 and 2019. Categories are based upon internal classifications.

	Three Months Ended March 31,
	2020				2019
	Net Sales		Percentage of Total Net Sales		Net Sales		Percentage of Total Net Sales
Notebooks/Mobile Devices	$	1,111.0	25.3	%	$	916.1	23.1	%
Netcomm Products	456.4		10.4		511.4		12.9
Desktops	384.3		8.8		297.0		7.5
Video	314.6		7.2		271.3		6.9
Enterprise and Data Storage (Including Drives)	240.5		5.5		293.3		7.4
Other Hardware	949.7		21.5		857.2		21.7
Total Hardware	3,456.5		78.7		3,146.3		79.5
Software(1)	666.3		15.2		593.0		15.0
Services(1)	230.6		5.3		189.0		4.8
Other(2)	35.8		0.8		29.6		0.7
Total Net sales	$	4,389.2	100.0	%	$	3,957.9	100.0	%

(1) 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.

(2) Includes items such as delivery charges to customers.