SIGNIFICANT ACCOUNTING POLICIES - AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 25, 2017	Jun. 26, 2016	Jun. 25, 2017	Jun. 26, 2016
Changes in accumulated other comprehensive loss
Balance at the beginning of the period			$ (461,515)
Other comprehensive income (loss) before reclassifications			4,046
Amounts reclassified from AOCL			5,141
Other comprehensive income	$ 6,544	$ 2,679	9,187	$ 4,486
Balance at the end of the period	(452,328)		(452,328)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Retirement benefit expense	3,328	3,694	6,655	7,388
Benefit for income taxes	(21,080)	(4,731)	(76,529)	(14,846)
Net of tax	37,446	14,734	133,021	27,475
Minimum Pension and Post-Retirement Liability
Changes in accumulated other comprehensive loss
Balance at the beginning of the period			(450,506)
Amounts reclassified from AOCL			5,141
Other comprehensive income			5,141
Balance at the end of the period	(445,365)		(445,365)
Minimum Pension and Post-Retirement Liability | Amount Reclassified from AOCI
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Retirement benefit expense	4,284	3,837	8,569	7,674
Benefit for income taxes	(1,714)	(1,535)	(3,428)	(3,070)
Net of tax	2,570	$ 2,302	5,141	$ 4,604
Other Comprehensive Loss Related to Equity Investments
Changes in accumulated other comprehensive loss
Balance at the beginning of the period			(11,009)
Other comprehensive income (loss) before reclassifications			4,046
Other comprehensive income			4,046
Balance at the end of the period	$ (6,963)		$ (6,963)