PENSION AND OTHER POSTRETIREMENT BENEFITS (Schedule of Defined Benefit Plan Obligations and Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2021	Jun. 28, 2020	Jun. 27, 2021	Jun. 28, 2020	Dec. 27, 2020	Dec. 29, 2019
Change in plan assets
Fair value of plan assets, beginning of period			$ 305,983
Fair value of plan assets, end of period	$ 327,307		327,307
Pension Benefits
Change in projected benefit obligation
Projected benefit obligation, beginning of period			404,194	$ 369,066
Interest cost	987	$ 2,011	2,437	4,050
Actuarial loss (gain)			(28,552)	28,806
Benefits paid			(5,978)	(9,965)
Curtailments and settlements			(2,689)	0
Prior service cost			0	11
Currency translation loss (gain)			10,196	(11,001)
Projected benefit obligation, end of period	379,608	380,967	379,608	380,967
Change in plan assets
Fair value of plan assets, beginning of period			305,983	294,589
Actual return on plan assets			14,564	(9,948)
Contributions by employer			6,832	5,173
Benefits paid			(5,978)	(9,965)
Curtailments and settlements			(2,689)	0
Expenses paid from assets			(169)	(526)
Currency translation gain (loss)			8,764	(9,849)
Fair value of plan assets, end of period	327,307	269,474	327,307	269,474
Funded status
Unfunded benefit obligation, end of period	(52,301)		(52,301)		$ (98,211)
Amounts recognized in the Condensed Consolidated Balance Sheets at end of period
Current liability	(819)		(819)		(7,510)
Long-term liability	(51,482)		(51,482)		(90,701)
Recognized liability	(52,301)		(52,301)		(98,211)
Amounts recognized in accumulated other comprehensive loss at end of period
Net actuarial loss	55,846	102,530	55,846	102,530	95,522	$ 58,239
Other Benefits
Change in projected benefit obligation
Projected benefit obligation, beginning of period			1,593	1,527
Interest cost	3	9	8	18
Actuarial loss (gain)			(35)	64
Benefits paid			(70)	(80)
Curtailments and settlements			0	0
Prior service cost			0	0
Currency translation loss (gain)			0	0
Projected benefit obligation, end of period	1,496	1,529	1,496	1,529
Change in plan assets
Fair value of plan assets, beginning of period			0	0
Actual return on plan assets			0	0
Contributions by employer			70	80
Benefits paid			(70)	(80)
Curtailments and settlements			0	0
Expenses paid from assets			0	0
Currency translation gain (loss)			0	0
Fair value of plan assets, end of period	0	0	0	0
Funded status
Unfunded benefit obligation, end of period	(1,496)		(1,496)		(1,593)
Amounts recognized in the Condensed Consolidated Balance Sheets at end of period
Current liability	(167)		(167)		(169)
Long-term liability	(1,329)		(1,329)		(1,424)
Recognized liability	(1,496)		(1,496)		(1,593)
Amounts recognized in accumulated other comprehensive loss at end of period
Net actuarial loss	$ 138	$ 155	$ 138	$ 155	$ 174	$ 91