REVENUE FROM CONTRACTS WITH CUSTOMERS - Disaggregation of Revenues by Major Business Line (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 25, 2022	Jun. 26, 2021	Jun. 25, 2022	Jun. 26, 2021
Disaggregation of Revenue [Line Items]
Total revenue	$ 973,131	$ 914,607	$ 1,887,060	$ 1,739,173
RMS
Disaggregation of Revenue [Line Items]
Total revenue	186,410	176,694	362,952	353,604
RMS | Services and products transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	85,803	66,334	155,727	131,230
RMS | Services and products transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	100,607	110,360	207,225	222,374
DSA
Disaggregation of Revenue [Line Items]
Total revenue	591,917	540,094	1,136,176	1,041,272
DSA | Services and products transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	589,371	539,790	1,131,707	1,040,258
DSA | Services and products transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	2,546	304	4,469	1,014
Manufacturing
Disaggregation of Revenue [Line Items]
Total revenue	194,804	197,819	387,932	344,297
Manufacturing | Services and products transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	92,811	95,974	187,820	146,542
Manufacturing | Services and products transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	$ 101,993	$ 101,845	$ 200,112	$ 197,755