Share-Based Compensation Arrangement By Share-Based Payment Award, Number Of Employees Affected By Modification

No definition available.

Name:	ilmn_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfEmployeesAffectedByModification
Namespace Prefix:	ilmn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=122041274&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of additional cost recognized for award under share-based payment arrangement from occurrence of event accelerating recognition of cost.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

An excess of the fair value of the modified award over the fair value of the award immediately before the modification.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)(iii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationIncrementalCompensationCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_ResearchAndDevelopmentExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_SellingGeneralAndAdministrativeExpensesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=ilmn_GRAILIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=ilmn_ReplacementAwardsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=ilmn_PerformanceSharesGrantedIn2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=ilmn_PerformanceSharesGrantedIn2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Stockholders' Equity - Narrative- Share-based Compensation (Details) $ in Millions	1 Months Ended		12 Months Ended
	Feb. 28, 2021 USD ($) employee	Aug. 31, 2020 employee	Jan. 02, 2022 USD ($)	Jan. 03, 2021 USD ($)	Dec. 29, 2019 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense, before taxes			$ 941	$ 194	$ 194
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense, before taxes			276	74	66
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense, before taxes			638	95	$ 105
GRAIL Inc
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment arrangement, accelerated cost			615
Replacement Awards \| GRAIL Inc
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment arrangement, accelerated cost			615
Share-based compensation expense, before taxes			24
Replacement Awards \| GRAIL Inc \| Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment arrangement, accelerated cost			167
Replacement Awards \| GRAIL Inc \| Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment arrangement, accelerated cost			$ 448
PSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation vesting performance period	3 years	3 years	3 years
Number of employees effected by modification \| employee		49
Incremental share-based compensation cost				$ 47
Performance Shares, Granted In 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of employees effected by modification \| employee	52
Incremental share-based compensation cost	$ 41
Performance Shares, Granted In 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of employees effected by modification \| employee	72
Incremental share-based compensation cost	$ 65