STOCKHOLDERS' EQUITY (Schedule of Changes in Unrealized Actuarial Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2015	Jun. 29, 2014	Jun. 28, 2015	Jun. 29, 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			6,544	(9,363)
Amounts reclassified from accumulated other comprehensive loss to net income			159	(81)
Total other comprehensive income (loss), net of tax	$ 8,791	$ (3,622)	6,703	(9,444)
Balance, end of period	(55,838)	(55,179)	(55,838)	(55,179)
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			6,501	(9,432)
Amounts reclassified from accumulated other comprehensive loss to net income			222	17
Total other comprehensive income (loss), net of tax			6,723	(9,415)
Balance, end of period	(55,849)	(55,212)	(55,849)	(55,212)
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			43	69
Amounts reclassified from accumulated other comprehensive loss to net income			(63)	(98)
Total other comprehensive income (loss), net of tax			(20)	(29)
Balance, end of period	$ 11	$ 33	$ 11	$ 33