Receivables, Contract Liabilities and Performance Obligations - Summary of Changes in Contract Liabilities from Contract with Customers (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2022 USD ($)
Contract with Customer, Contract Asset, Contract Liability, and Receivable Increase (Decrease) [Roll Forward]
Beginning balance	$ 116,067
Reclassification of the beginning contract liabilities to revenue, as the result of performance obligations satisfied	(31,452)
Cash received in advance and not recognized as revenue	35,607
Ending balance	$ 120,222

Contract with Customer, Contract Asset, Contract Liability, and Receivable Increase (Decrease)

No definition available.

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Namespace Prefix:	nsit_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Contract with customer, liability, cash received in advance and not recognized as revenue.

+ References

No definition available.

+ Details

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Namespace Prefix:	nsit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123360276&loc=SL49130531-203044

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130549-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=123360276&loc=SL49130532-203044

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of revenue recognized arising from contract liability from change in timeframe for performance obligation to be satisfied.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130551-203045

+ Details

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