STOCKHOLDERS' EQUITY (Schedule of Changes in Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 25, 2017	Jun. 26, 2016	Jun. 25, 2017	Jun. 26, 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			290	(127)
Total other comprehensive loss, net of tax	$ (3,814)	$ (1,941)	(2,492)	(8,796)
Balance	1,210,097	818,693	1,210,097	818,693
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			(2,782)	(8,669)
Amounts reclassified from accumulated other comprehensive loss to net income			290	(127)
Total other comprehensive loss, net of tax			(2,492)	(8,796)
Balance	(66,735)	(67,726)	(66,735)	(67,726)
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			(2,782)	(8,934)
Amounts reclassified from accumulated other comprehensive loss to net income			290	205
Total other comprehensive loss, net of tax			(2,492)	(8,729)
Balance	(66,735)	(67,726)	(66,735)	(67,726)
Unrealized Holding Gains on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance			0	67
Other comprehensive income (loss) before reclassifications			0	265
Amounts reclassified from accumulated other comprehensive loss to net income			0	(332)
Total other comprehensive loss, net of tax			0	(67)
Balance	$ 0	$ 0	$ 0	$ 0