EMPLOYEE BENEFITS (Details) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 29, 2016 USD ($)	Jun. 26, 2016 USD ($)	Jun. 28, 2015 USD ($)	Jun. 26, 2016 USD ($) item	Jun. 28, 2015 USD ($)
EMPLOYEE BENEFITS
Number of new participants | item				0
Retirement expense for continuing operations
Net pension expense		$ 3,694	$ 2,493	$ 7,388	$ 4,986
Pension plan
Retirement expense for continuing operations
Service cost		4,700	2,920	9,400	5,840
Interest cost		22,167	21,249	44,334	42,497
Expected return on plan assets		(27,108)	(26,570)	(54,215)	(53,141)
Actuarial loss		4,595	5,548	9,191	11,097
Net pension expense		4,354	3,147	8,710	6,293
Value of contributions to plan	$ 47,100
Post-retirement plans
Retirement expense for continuing operations
Net pension expense		$ (660)	$ (654)	$ (1,322)	$ (1,307)