BUSINESS COMBINATIONS AND DIVESTITURE - Pro Forma Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Citoxlab
Business Acquisition [Line Items]
Revenue	$ 2,683,610	$ 2,442,283
Net income attributable to common shareholders	$ 268,995	233,288
MPI Research
Business Acquisition [Line Items]
Revenue		2,328,213	$ 2,095,385
Net income attributable to common shareholders		$ 225,550	$ 126,641