v3.8.0.1

Organization and Summary of Significant Accounting Policies - Narrative - Revenue Recognition (Details) | 12 Months Ended
--- | ---
Dec. 31, 2017
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |
Period of time average selling prices are observed to establish best estimate of selling price | 12 months
Minimum [Member] |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |
Product or service delivery period | 3 months
Maximum [Member] |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |
Product or service delivery period | 6 months

X
- Definition Revenue Recognition, Multiple-Deliverable Arrangements, Delivery Time Frame + References No definition available. + Details
Name: | ilmn_RevenueRecognitionMultipleDeliverableArrangementsDeliveryTimeFrame
Namespace Prefix: | ilmn_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Revenue Recognition, Multiple-Deliverable Arrangements, Determination of Selling Price, Period + References No definition available. + Details
Name: | ilmn_RevenueRecognitionMultipleDeliverableArrangementsDeterminationofSellingPricePeriod
Namespace Prefix: | ilmn_
Data Type: | xbrli:durationItemType
Balance Type: | na
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_RevenueRecognitionMultipleDeliverableArrangementsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |