Intangible Assets - Summary of Identifiable Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Jan. 01, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 448	$ 475
Accumulated Amortization	(273)	(238)
Finite-Lived Intangible Assets, Net	175	237
Licensed technologies [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	95	95
Accumulated Amortization	(74)	(64)
Finite-Lived Intangible Assets, Net	21	31
Core technologies [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	300	328
Accumulated Amortization	(161)	(142)
Finite-Lived Intangible Assets, Net	139	186
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	32	33
Accumulated Amortization	(25)	(22)
Finite-Lived Intangible Assets, Net	7	11
License agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	14	14
Accumulated Amortization	(8)	(7)
Finite-Lived Intangible Assets, Net	6	7
Trade name [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7	5
Accumulated Amortization	(5)	(3)
Finite-Lived Intangible Assets, Net	$ 2	$ 2

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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

- Definition

Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=ilmn_LicensedTechnologyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_DevelopedTechnologyRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_LicensingAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_TradeNamesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: