STOCKHOLDERS' EQUITY (Schedule of Changes in Unrealized Actuarial Losses) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 29, 2015	Mar. 30, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	$ (62,541)	$ (45,735)
Other comprehensive income (loss) before reclassifications	(2,148)	(5,806)
Amounts reclassified from accumulated other comprehensive loss to net income	60	(16)
Total other comprehensive loss, net of tax	(2,088)	(5,822)
Balance, end of period	(64,629)	(51,557)
Losses Related to Pension and Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	(62,572)	(45,797)
Other comprehensive income (loss) before reclassifications	(2,180)	(5,795)
Amounts reclassified from accumulated other comprehensive loss to net income	111	9
Total other comprehensive loss, net of tax	(2,069)	(5,786)
Balance, end of period	(64,641)	(51,583)
Unrealized Holding Gains on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of period	31	62
Other comprehensive income (loss) before reclassifications	32	(11)
Amounts reclassified from accumulated other comprehensive loss to net income	(51)	(25)
Total other comprehensive loss, net of tax	(19)	(36)
Balance, end of period	$ 12	$ 26