STOCKHOLDERS' EQUITY (Schedule of Changes in Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 26, 2017	Mar. 27, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	$ 896,747	$ 1,261,810
Amounts reclassified from accumulated other comprehensive loss to net income	145	(38)
Total other comprehensive income (loss), net of tax	1,322	(6,855)
Balance	979,351	1,371,189
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	(64,243)	(58,930)
Other comprehensive income (loss) before reclassifications		(6,817)
Amounts reclassified from accumulated other comprehensive loss to net income		(38)
Total other comprehensive income (loss), net of tax	1,322	(6,855)
Balance	(62,921)	(65,785)
Losses Related to Pension and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	(64,243)	(58,997)
Other comprehensive income (loss) before reclassifications	1,177	(6,988)
Amounts reclassified from accumulated other comprehensive loss to net income	145	103
Total other comprehensive income (loss), net of tax	1,322	(6,885)
Balance	$ (62,921)	(65,882)
Unrealized Holding Gains on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance		67
Other comprehensive income (loss) before reclassifications		171
Amounts reclassified from accumulated other comprehensive loss to net income		(141)
Total other comprehensive income (loss), net of tax		30
Balance		$ 97