EMPLOYEE BENEFITS - Retirement and Post retirement costs - (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2018	Sep. 30, 2018	Sep. 24, 2017	Sep. 30, 2018	Sep. 24, 2017
Retirement expense for continuing operations
Net pension expense		$ 2,778	$ 3,328	$ 8,335	$ 9,983
Matching contributions		600		1,900
Pension plan
Retirement expense for continuing operations
Interest cost		19,788	21,367	59,365	64,101
Expected return on plan assets		(22,624)	(22,392)	(67,872)	(67,177)
Actuarial loss		6,295	5,084	18,886	15,252
Net pension expense		3,459	4,059	10,379	12,176
Proceeds from sale of real property location	$ 4,100
(Loss) on sale of real property location				(200)
Post-retirement plans
Retirement expense for continuing operations
Net pension expense		$ (681)	$ (731)	$ (2,044)	$ (2,193)