GOODWILL AND INTANGIBLE ASSETS - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 27, 2021	Dec. 26, 2020
Other intangible assets
Gross	$ 1,327,743	$ 1,334,244
Accumulated Amortization	(532,178)	(546,645)
Net	795,565	787,599
Backlog
Other intangible assets
Gross	610	29,233
Accumulated Amortization	(152)	(29,233)
Net	458	0
Technology
Other intangible assets
Gross	133,667	130,907
Accumulated Amortization	(85,610)	(81,305)
Net	48,057	49,602
Trademarks and trade names
Other intangible assets
Gross	12,231	15,870
Accumulated Amortization	(2,112)	(5,648)
Net	10,119	10,222
Other
Other intangible assets
Gross	28,736	20,903
Accumulated Amortization	(4,189)	(14,633)
Net	24,547	6,270
Other intangible assets
Other intangible assets
Gross	175,244	196,913
Accumulated Amortization	(92,063)	(130,819)
Net	83,181	66,094
Client relationships
Other intangible assets
Gross	1,152,499	1,137,331
Accumulated Amortization	(440,115)	(415,826)
Net	$ 712,384	$ 721,505