EMPLOYEE BENEFITS - Retirement and Post retirement costs - (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2018	Jul. 01, 2018	Jun. 25, 2017	Jul. 01, 2018	Jun. 25, 2017
Retirement expense for continuing operations
Net pension expense		$ 2,779	$ 3,328	$ 5,557	$ 6,655
Matching contributions		600		1,300
Pension plan
Retirement expense for continuing operations
Interest cost		19,789	21,367	39,577	42,734
Expected return on plan assets		(22,624)	(22,393)	(45,248)	(44,785)
Actuarial loss		6,296	5,084	12,591	10,168
Net pension expense		3,461	4,058	6,920	8,117
Proceeds from sale of real property location	$ 4,100
(Loss) on sale of real property location		(200)		(200)
Post-retirement plans
Retirement expense for continuing operations
Net pension expense		$ (682)	$ (730)	$ (1,363)	$ (1,462)