SEGMENT INFORMATION - Operating Performance and Assets by Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 29, 2024	Oct. 01, 2023	Sep. 29, 2024	Oct. 01, 2023
Segment Reporting Information [Line Items]
Consolidated revenue	$ 1,080	$ 1,119	$ 3,268	$ 3,382
Consolidated income (loss) from operations	741	(754)	(1,008)	(905)
Operating Segments | Core Illumina
Segment Reporting Information [Line Items]
Consolidated revenue	1,080	1,106	3,228	3,341
Consolidated income (loss) from operations	741	262	1,298	519
Operating Segments | GRAIL
Segment Reporting Information [Line Items]
Consolidated revenue	0	21	55	62
Consolidated income (loss) from operations	0	(1,015)	(2,305)	(1,424)
Eliminations
Segment Reporting Information [Line Items]
Consolidated revenue	0	(8)	(15)	(21)
Consolidated income (loss) from operations	$ 0	$ (1)	$ (1)	$ 0