STOCKHOLDERS' EQUITY (Schedule of Changes in Unrealized Actuarial Losses) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 28, 2014	Dec. 29, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	$ (45,735)	$ (68,511)
Other comprehensive income (loss) before reclassifications	(16,491)	21,775
Amounts reclassified from accumulated other comprehensive loss to net income	(315)	1,001
Net current year other comprehensive income (loss)	(16,806)	22,776
Balance, end of year	(62,541)	(45,735)
Pension and Other Postretirement Plans Costs [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	(45,797)	(68,511)
Other comprehensive income (loss) before reclassifications	(16,810)	21,713
Amounts reclassified from accumulated other comprehensive loss to net income	35	1,001
Net current year other comprehensive income (loss)	(16,775)	22,714
Balance, end of year	(62,572)	(45,797)
Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	62	0
Other comprehensive income (loss) before reclassifications	319	62
Amounts reclassified from accumulated other comprehensive loss to net income	(350)	0
Net current year other comprehensive income (loss)	(31)	62
Balance, end of year	$ 31	$ 62