PENSION AND OTHER POSTRETIREMENT BENEFITS (Schedule of Unrecognized Benefit Amounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Pension Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net actuarial loss (gain), beginning of year	$ 46,494	$ 38,115	$ 43,907
Amortization	(932)	(659)	(714)
Settlement adjustments	0	(2,064)	(3,843)
Actuarial loss (gain)	15,745	10,305	(10,944)
Asset loss (gain)	(7,072)	797	9,709
Net actuarial loss (gain), end of year	54,235	46,494	38,115
Other Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net actuarial loss (gain), beginning of year	(31)	(79)	(127)
Amortization	0	0	0
Settlement adjustments	(2)	2	4
Actuarial loss (gain)	68	46	44
Asset loss (gain)	0	0	0
Net actuarial loss (gain), end of year	$ 35	$ (31)	$ (79)