Segment Information - Narrative (Details)	6 Months Ended
Jun. 30, 2022 segment employee
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

Number of Operating Segments, Reportable Unit Quantitative Threshold Not Met

No definition available.

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- Definition

Segment Reporting, Customer Segments, Customer Employee Headcount

+ References

No definition available.

+ Details

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Namespace Prefix:	cdw_
Data Type:	xbrli:integerItemType
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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8672-108599

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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