SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Pension Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Net periodic (benefit) expense:
Interest cost	$ 4,400	$ 4,676	$ 13,602	$ 13,475
Expected return on plan assets	(5,704)	(5,277)	(17,633)	(15,208)
Amortization of actuarial loss	750	768	2,318	2,214
Net periodic expense (benefit)	$ (554)	$ 167	$ (1,713)	$ 481