SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Pension Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Net periodic (benefit) expense:
Interest cost	$ 4,075	$ 4,400	$ 12,602	$ 13,602
Expected return on plan assets	(4,815)	(5,704)	(14,893)	(17,633)
Amortization of actuarial loss	617	750	1,909	2,318
Net periodic expense (benefit)	$ (123)	$ (554)	$ (382)	$ (1,713)