Segment Information - Summary of Operating Performance and Assets by Segment (Details) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 02, 2022 USD ($)	Oct. 03, 2021 USD ($)	Oct. 02, 2022 USD ($) segment	Oct. 03, 2021 USD ($)	Jan. 02, 2022 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment			2
Segment Reporting Information [Line Items]
Consolidated revenue	$ 1,115	$ 1,108	$ 3,501	$ 3,327
Consolidated loss from operations	(3,657)	(545)	(4,052)	(164)
Consolidated total assets	11,256		11,256		$ 15,217
Operating Segments | Core Illumina
Segment Reporting Information [Line Items]
Consolidated revenue	1,110	1,106	3,487	3,325
Consolidated loss from operations	445	205	411	586
Consolidated total assets	5,626		5,626		5,571
Operating Segments | GRAIL
Segment Reporting Information [Line Items]
Consolidated revenue	10	2	32	2
Consolidated loss from operations	(4,101)	(750)	(4,460)	(750)
Consolidated total assets	5,637		5,637		9,649
Eliminations
Segment Reporting Information [Line Items]
Consolidated revenue	(5)	0	(18)	0
Consolidated loss from operations	(1)	$ 0	(3)	$ 0
Consolidated total assets	$ (7)		$ (7)		$ (3)