PENSION AND OTHER POSTRETIREMENT BENEFITS (Schedule of Unrecognized Benefit Amounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2020	Dec. 29, 2019	Dec. 30, 2018
Pension Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net actuarial loss (gain), beginning of year	$ 58,239	$ 54,343	$ 54,235
Amortization	(1,503)	(1,313)	(1,203)
Settlement adjustments	(3,371)	(3,538)	0
Actuarial loss (gain)	38,822	20,729	(15,635)
Asset loss (gain)	400	(11,982)	16,946
Net prior service cost	378	0	0
Currency translation loss	2,557	0	0
Net actuarial loss (gain), end of year	95,522	58,239	54,343
Other Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net actuarial loss (gain), beginning of year	91	(34)	35
Amortization	0	0	0
Settlement adjustments	(7)	(7)	3
Actuarial loss (gain)	90	132	(72)
Asset loss (gain)	0	0	0
Net prior service cost	0	0	0
Currency translation loss	0	0	0
Net actuarial loss (gain), end of year	$ 174	$ 91	$ (34)