PENSION AND OTHER POSTRETIREMENT BENEFITS (Schedule of Unrecognized Benefit Amounts) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 26, 2017	Mar. 27, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Actuarial loss (gain)	$ (1,322)	$ 6,885
Pension Benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net actuarial loss (gain), beginning of period	46,494	38,115
Amortization	(233)	(165)
Curtailment and settlement adjustments	0	0
Actuarial loss (gain)	785	4,417
Asset loss (gain)	(2,652)	6,759
Net actuarial loss (gain), end of period	44,394	49,126
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)	(24)	51
Asset loss (gain)	0	0
Net actuarial loss (gain), end of period	$ (55)	$ (28)