STOCKHOLDERS' EQUITY (Schedule of Changes in Unrealized Actuarial Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 27, 2016	Mar. 29, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	$ (58,930)	$ (62,541)
Other comprehensive income (loss) before reclassifications	(6,817)	(2,148)
Amounts reclassified from accumulated other comprehensive loss to net income	(38)	60
Total other comprehensive loss, net of tax	(6,855)	(2,088)
Balance, end of period	(65,785)	(64,629)
Losses Related to Pension and Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	(58,997)	(62,572)
Other comprehensive income (loss) before reclassifications	(6,988)	(2,180)
Amounts reclassified from accumulated other comprehensive loss to net income	103	111
Total other comprehensive loss, net of tax	(6,885)	(2,069)
Balance, end of period	(65,882)	(64,641)
Unrealized Holding Gains on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	67	31
Other comprehensive income (loss) before reclassifications	171	32
Amounts reclassified from accumulated other comprehensive loss to net income	(141)	(51)
Total other comprehensive loss, net of tax	30	(19)
Balance, end of period	$ 97	$ 12