PENSION AND OTHER POSTRETIREMENT BENEFITS (Schedule of Defined Benefit Plan Obligations and Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2015	Dec. 28, 2014	Dec. 29, 2013	Dec. 30, 2012
Change in plan assets:
Fair value of plan assets, beginning of year	$ 113,552
Fair value of plan assets, end of year	96,947	$ 113,552
Pension Benefits [Member]
Change in projected benefit obligation:
Projected benefit obligation, beginning of year	190,401	170,030
Interest cost	7,754	8,103	$ 7,954
Actuarial losses (gains)	(10,944)	24,670
Benefits paid	(6,074)	(12,154)
Settlements	(15,185)	(248)
Projected benefit obligation, end of year	165,952	190,401	170,030
Change in plan assets:
Fair value of plan assets, beginning of year	113,552	108,496
Actual return on plan assets	(3,024)	3,944
Contributions by employer	7,678	13,514
Benefits paid	(6,074)	(12,154)
Settlements	(15,185)	(248)
Fair value of plan assets, end of year	96,947	113,552	108,496
Funded status:
Unfunded benefit obligation, end of year	(69,005)	(76,849)
Amounts recognized in the Consolidated Balance Sheets at end of year:
Current liability	(10,779)	(9,373)
Long-term liability	(58,226)	(67,476)
Recognized liability	(69,005)	(76,849)
Amounts recognized in accumulated other comprehensive loss at end of year:
Net actuarial loss (gain)	38,115	43,907	16,957	$ 53,368
Other Benefits [Member]
Change in projected benefit obligation:
Projected benefit obligation, beginning of year	1,657	1,705
Interest cost	67	81
Actuarial losses (gains)	44	(10)
Benefits paid	0	0
Settlements	(96)	(119)
Projected benefit obligation, end of year	1,672	1,657	1,705
Change in plan assets:
Fair value of plan assets, beginning of year	0	0
Actual return on plan assets	0	0
Contributions by employer	96	119
Benefits paid	0	0
Settlements	(96)	(119)
Fair value of plan assets, end of year	0	0	0
Funded status:
Unfunded benefit obligation, end of year	(1,672)	(1,657)
Amounts recognized in the Consolidated Balance Sheets at end of year:
Current liability	(138)	(129)
Long-term liability	(1,534)	(1,528)
Recognized liability	(1,672)	(1,657)
Amounts recognized in accumulated other comprehensive loss at end of year:
Net actuarial loss (gain)	$ (79)	$ (127)	$ (126)	$ (49)