SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Pension Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Net periodic (benefit) expense:
Interest cost	$ 4,182	$ 4,486	$ 8,527	$ 9,202
Expected return on plan assets	(4,943)	(5,815)	(10,078)	(11,929)
Amortization of actuarial loss	634	764	1,292	1,568
Net periodic expense (benefit)	$ (127)	$ (565)	$ (259)	$ (1,159)