Cover Page - USD ($) shares in Millions, $ in Billions	12 Months Ended
	Jan. 03, 2021	Feb. 12, 2021	Jun. 26, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Jan. 03, 2021
Current Fiscal Year End Date	--01-03
Document Transition Report	false
Entity File Number	001-35406
Entity Registrant Name	Illumina, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0804655
Entity Address, Address Line One	5200 Illumina Way
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92122
City Area Code	858
Local Phone Number	202-4500
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	ILMN
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		145.9
Entity Public Float			$ 46.2
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement for the 2021 annual meeting of stockholders are incorporated by reference into Items 10 through 14 of Part III of this Report
Entity Central Index Key	0001110803
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false