v3.8.0.1

Balance Sheet Account Details - Narrative - Property and Equipment (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Jan. 01, 2017 | Jan. 03, 2016
Property, Plant and Equipment [Line Items] |  |  |
Non-cash expenditures included in property and equipment, net | $ 117 | $ 220 | $ 24
Construction In Progress And Build to Suit Lease Liability [Member] |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Non-cash expenditures included in property and equipment, net | $ 79 | $ 193 | $ 10

X
- Definition Future cash outflow to pay for purchases of fixed assets that have occurred. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586 + Details
Name: | us-gaap_CapitalExpendituresIncurredButNotYetPaid
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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_PropertyPlantAndEquipmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=ilmn_ConstructionInProgressAndBuildtoSuitLeaseLiabilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |