PENSION AND OTHER POSTRETIREMENT BENEFITS (Schedule of Unrecognized Benefit Amounts) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 25, 2017	Jun. 26, 2016	Jun. 25, 2017	Jun. 26, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Actuarial loss (gain)	$ 3,814	$ 1,844	$ 2,492	$ 8,729
Pension Benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net actuarial loss (gain), beginning of period			46,494	38,115
Amortization			(466)	(329)
Curtailment and settlement adjustments			0	0
Actuarial loss (gain)			8,885	12,736
Asset loss (gain)			(4,515)	1,543
Net actuarial loss (gain), end of period	50,398	52,065	50,398	52,065
Other Benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net actuarial loss (gain), beginning of period			(31)	(79)
Amortization			0	0
Curtailment and settlement adjustments			0	0
Actuarial loss (gain)			101	72
Asset loss (gain)			0	0
Net actuarial loss (gain), end of period	$ 70	$ (7)	$ 70	$ (7)