PENSION AND OTHER POSTRETIREMENT BENEFITS (Schedule of Net Periodic Benefit Cost (Income)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Interest cost	$ 5,571	$ 5,585	$ 7,754
Estimated return on plan assets	(5,254)	(5,256)	(6,684)
Settlement loss (gain)	0	2,064	3,843
Amortization of net loss	932	659	714
Net cost	1,249	3,052	5,627
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Interest cost	51	51	67
Estimated return on plan assets	0	0	0
Settlement loss (gain)	2	(2)	(4)
Amortization of net loss	0	0	0
Net cost	$ 53	$ 49	$ 63