PENSION AND OTHER POSTRETIREMENT BENEFITS (Schedule of Defined Benefit Plan Obligations and Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 25, 2016	Dec. 27, 2015	Dec. 28, 2014	Dec. 29, 2013
Change in plan assets:
Fair value of plan assets, beginning of year	$ 96,947
Fair value of plan assets, end of year	97,526	$ 96,947
Pension Benefits [Member]
Change in projected benefit obligation:
Projected benefit obligation, beginning of year	165,952	190,401
Interest cost	5,585	7,754	$ 8,103
Actuarial losses (gains)	10,305	(10,944)
Benefits paid	(6,098)	(6,074)
Settlements	(8,585)	(15,185)
Projected benefit obligation, end of year	167,159	165,952	190,401
Change in plan assets:
Fair value of plan assets, beginning of year	96,947	113,552
Actual return on plan assets	4,460	(3,024)
Contributions by employer	10,802	7,678
Benefits paid	(6,098)	(6,074)
Settlements	(8,585)	(15,185)
Fair value of plan assets, end of year	97,526	96,947	113,552
Funded status:
Unfunded benefit obligation, end of year	(69,633)	(69,005)
Amounts recognized in the Consolidated Balance Sheets at end of year:
Current liability	(13,113)	(10,779)
Long-term liability	(56,520)	(58,226)
Recognized liability	(69,633)	(69,005)
Amounts recognized in accumulated other comprehensive loss at end of year:
Net actuarial loss (gain)	46,494	38,115	43,907	$ 16,957
Other Benefits [Member]
Change in projected benefit obligation:
Projected benefit obligation, beginning of year	1,672	1,657
Interest cost	51	67
Actuarial losses (gains)	46	44
Benefits paid	0	0
Settlements	(121)	(96)
Projected benefit obligation, end of year	1,648	1,672	1,657
Change in plan assets:
Fair value of plan assets, beginning of year	0	0
Actual return on plan assets	0	0
Contributions by employer	121	96
Benefits paid	0	0
Settlements	(121)	(96)
Fair value of plan assets, end of year	0	0	0
Funded status:
Unfunded benefit obligation, end of year	(1,648)	(1,672)
Amounts recognized in the Consolidated Balance Sheets at end of year:
Current liability	(147)	(138)
Long-term liability	(1,501)	(1,534)
Recognized liability	(1,648)	(1,672)
Amounts recognized in accumulated other comprehensive loss at end of year:
Net actuarial loss (gain)	$ (31)	$ (79)	$ (127)	$ (126)