v3.8.0.1
Document and Entity Information - shares
shares in Millions
3 Months Ended
Apr. 01, 2018
Apr. 20, 2018
Document and Entity Information [Abstract]    
Entity Registrant Name Illumina Inc  
Entity Central Index Key 0001110803  
Current Fiscal Year End Date --12-30  
Entity Filer Category Large Accelerated Filer  
Document Type 10-Q  
Document Period End Date Apr. 01, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Entity Common Stock, Shares Outstanding   147