EMPLOYEE BENEFITS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2015	Dec. 28, 2014	Dec. 29, 2013	Dec. 27, 2015	Dec. 28, 2014
Changes in the fair value of the plan's Level 3 investment assets
Fair value of plan assets, end of year	$ 1,349,603
Funded Status
Fair value of plan assets	1,349,603			$ 1,349,603
Amounts recognized in the statement of financial position consist of:
Noncurrent liability				(581,852)	$ (574,024)
Pension plan
Change in Benefit Obligation
Benefit obligation, beginning of year	2,051,907	$ 1,849,321
Service cost	11,680	8,030	$ 5,545
Interest cost	84,994	91,004	84,596
Actuarial (gain)/loss	(101,952)	213,176
Gross benefits paid	(103,062)	(101,441)
Administrative expenses	(12,247)	(8,183)
Benefit obligation, end of year	1,931,320	2,051,907	1,849,321
Changes in the fair value of the plan's Level 3 investment assets
Fair value of plan assets, beginning of year	1,478,686	1,432,695
Actual return on plan assets	(22,307)	122,133
Employer contribution	8,533	33,482
Gross benefits paid	(103,062)	(101,441)
Administrative expenses	(12,247)	(8,183)
Fair value of plan assets, end of year	1,349,603	1,478,686	1,432,695
Funded Status
Fair value of plan assets	1,478,686	1,432,695	1,432,695	1,349,603	1,478,686
Benefit obligations	(2,051,907)	(1,849,321)	(1,849,321)	(1,931,320)	(2,051,907)
Funded status and amount recognized, end of year				(581,717)	(573,221)
Amounts recognized in the statement of financial position consist of:
Current liability				(8,450)	(8,529)
Noncurrent liability				(573,267)	(564,692)
Amounts recognized in the statement of financial position				(581,717)	(573,221)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss/(gain)				705,853	701,408
Amounts recognized in accumulated other comprehensive income				705,853	701,408
Supplemental retirement plans
Changes in the fair value of the plan's Level 3 investment assets
Employer contribution	8,500	8,500	8,300
Post-retirement plans
Change in Benefit Obligation
Benefit obligation, beginning of year	10,602	12,586
Interest cost	368	514
Plan participants' contributions	35	267
Actuarial (gain)/loss	(87)	467
Gross benefits paid	(1,035)	(1,611)
Plan amendment		(1,621)
Benefit obligation, end of year	9,883	10,602	12,586
Changes in the fair value of the plan's Level 3 investment assets
Employer contribution	1,000	1,344
Plan participants' contributions	35	267
Gross benefits paid	(1,035)	(1,611)
Funded Status
Benefit obligations	$ (10,602)	$ (12,586)	$ (12,586)	(9,883)	(10,602)
Funded status and amount recognized, end of year				(9,883)	(10,602)
Amounts recognized in the statement of financial position consist of:
Current liability				(1,298)	(1,270)
Noncurrent liability				(8,585)	(9,332)
Amounts recognized in the statement of financial position				(9,883)	(10,602)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss/(gain)				(8,568)	(9,385)
Prior service cost/(credit)				(10,690)	(12,768)
Amounts recognized in accumulated other comprehensive income				$ (19,258)	$ (22,153)