PENSION AND OTHER POSTRETIREMENT BENEFITS (Schedule of Unrecognized Benefit Amounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2015	Dec. 28, 2014	Dec. 29, 2013
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Actuarial loss (gain)	$ (3,575)	$ 16,775	$ (22,714)
Pension Benefits [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net actuarial loss (gain), beginning of year	43,907	16,957	53,368
Amortization	(714)	(56)	(1,001)
Settlement adjustments	(3,843)	(93)	0
Actuarial loss (gain)	(10,944)	24,670	(24,315)
Asset loss (gain)	9,709	2,429	(11,095)
Net actuarial loss (gain), end of year	38,115	43,907	16,957
Other Benefits [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net actuarial loss (gain), beginning of year	(127)	(126)	(49)
Amortization	0	0	0
Settlement adjustments	4	9	15
Actuarial loss (gain)	44	(10)	(92)
Asset loss (gain)	0	0	0
Net actuarial loss (gain), end of year	$ (79)	$ (127)	$ (126)