SIGNIFICANT ACCOUNTING POLICIES - AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jun. 25, 2017	Jul. 01, 2018	Jun. 25, 2017
Changes in stockholders' equity
Balance at the beginning of the period			$ (449,369)
Amounts reclassified from AOCL			11,099
Other comprehensive income	$ 5,549	$ 6,544	11,099	$ 9,187
Balance at the end of the period	(438,270)		(438,270)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Retirement benefit expense	2,779	3,328	5,557	6,655
Benefit for income taxes	3,618	(21,080)	11,490	(76,529)
Net of tax	20,365	37,446	59,306	133,021
Minimum Pension and Post-Retirement Liability
Changes in stockholders' equity
Balance at the beginning of the period			(442,406)
Amounts reclassified from AOCL			11,099
Other comprehensive income			11,099
Balance at the end of the period	(431,307)		(431,307)
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	5,549	4,284	11,099	8,569
Benefit for income taxes		(1,714)		(3,428)
Net of tax	5,549	$ 2,570	11,099	$ 5,141
Other Comprehensive Loss Related to Equity Investments
Changes in stockholders' equity
Balance at the beginning of the period			(6,963)
Balance at the end of the period	$ (6,963)		$ (6,963)