PENSION AND OTHER POSTRETIREMENT BENEFITS (Schedule of Plan Asset Allocations) (Details)	Jun. 27, 2021	Dec. 27, 2020
Defined Benefit Plan Disclosure [Line Items]
Total assets	100.00%	100.00%
Cash and cash equivalents | Union Plan
Defined Benefit Plan Disclosure [Line Items]
Total assets	2.00%	1.00%
Equity securities | Union Plan
Defined Benefit Plan Disclosure [Line Items]
Total assets	2.00%	2.00%
Equity securities | GK Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Total assets	20.00%	20.00%
Equity securities | U.K. Plans
Defined Benefit Plan Disclosure [Line Items]
Total assets	36.00%	35.00%
Fixed income securities | Union Plan
Defined Benefit Plan Disclosure [Line Items]
Total assets	2.00%	2.00%
Fixed income securities | GK Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Total assets	12.00%	13.00%
Fixed income securities | U.K. Plans
Defined Benefit Plan Disclosure [Line Items]
Total assets	19.00%	20.00%
Real estate | GK Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Total assets	1.00%	1.00%
Real estate | U.K. Plans
Defined Benefit Plan Disclosure [Line Items]
Total assets	6.00%	6.00%