PENSION AND OTHER POSTRETIREMENT BENEFITS (Schedule of Defined Benefit Plan Obligations and Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2016	Sep. 27, 2015	Sep. 25, 2016	Sep. 27, 2015	Dec. 27, 2015	Dec. 28, 2014
Change in plan assets:
Fair value of plan assets, beginning of period			$ 96,947
Fair value of plan assets, end of period	$ 103,425		103,425
Pension Benefits [Member]
Change in projected benefit obligation:
Projected benefit obligation, beginning of period			165,952	$ 190,401
Interest cost	1,396	$ 1,938	4,189	5,815
Actuarial losses (gains)			12,233	981
Benefits paid			(7,274)	(4,622)
Curtailments and settlements			0	(14,265)
Projected benefit obligation, end of period	175,100	178,310	175,100	178,310
Change in plan assets:
Fair value of plan assets, beginning of period			96,947	113,552
Actual return on plan assets			4,769	(3,822)
Contributions by employer			8,983	7,603
Benefits paid			(7,274)	(4,622)
Curtailments and settlements			0	(14,265)
Fair value of plan assets, end of period	103,425	98,446	103,425	98,446
Funded status:
Unfunded benefit obligation, end of period	(71,675)		(71,675)		$ (69,005)
Amounts recognized in the Condensed Consolidated Balance Sheets at end of period:
Current liability	(10,763)		(10,763)		(10,779)
Long-term liability	(60,912)		(60,912)		(58,226)
Recognized liability	(71,675)		(71,675)		(69,005)
Amounts recognized in accumulated other comprehensive loss at end of period:
Net actuarial loss (gain)	49,026	49,558	49,026	49,558	38,115	$ 43,907
Other Benefits [Member]
Change in projected benefit obligation:
Projected benefit obligation, beginning of period			1,672	1,657
Interest cost	12	16	38	50
Actuarial losses (gains)			95	(11)
Benefits paid			(105)	(96)
Curtailments and settlements			0	0
Projected benefit obligation, end of period	1,700	1,600	1,700	1,600
Change in plan assets:
Fair value of plan assets, beginning of period			0	0
Actual return on plan assets			0	0
Contributions by employer			105	96
Benefits paid			(105)	(96)
Curtailments and settlements			0	0
Fair value of plan assets, end of period	0	0	0	0
Funded status:
Unfunded benefit obligation, end of period	(1,700)		(1,700)		(1,672)
Amounts recognized in the Condensed Consolidated Balance Sheets at end of period:
Current liability	(139)		(139)		(138)
Long-term liability	(1,561)		(1,561)		(1,534)
Recognized liability	(1,700)		(1,700)		(1,672)
Amounts recognized in accumulated other comprehensive loss at end of period:
Net actuarial loss (gain)	$ 16	$ (138)	$ 16	$ (138)	$ (79)	$ (127)