EMPLOYEE BENEFITS - Assumptions (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Feb. 29, 2016	Dec. 31, 2016	Dec. 27, 2015	Dec. 28, 2014	Dec. 29, 2013
Pension plan
Weighted average assumptions used for valuing benefit obligations
Discount rate (as a percent)			4.71%	4.24%
Weighted average assumptions used in calculating expense
Expected long-term return on plan assets (as a percent)			7.75%	8.00%	8.00%
Discount rate (as a percent)			4.24%	5.01%	4.17%
Medical cost trend rates
Value of contributions to plan			$ 8,533	$ 33,482
Contribution				$ 25,000	$ 7,600
Gain or loss recognized on the contribution of property			0
Financing obligation from contribution of real property			32,400
Expected benefit payments
2016			101,524
2017			104,592
2018			107,158
2019			112,402
2020			113,173
2021-2025			612,003
Total			$ 1,150,852
Post-retirement plans
Weighted average assumptions used for valuing benefit obligations
Discount rate (as a percent)			4.21%	3.69%
Weighted average assumptions used in calculating expense
Discount rate (as a percent)			3.69%	4.36%	3.39%
Medical cost trend rates
Value of contributions to plan			$ 1,000	$ 1,344
Expected benefit payments
2016			1,297
2017			1,198
2018			1,105
2019			1,026
2020			942
2021-2025			3,567
Total			$ 9,135
Expected | Pension plan
Medical cost trend rates
Value of contributions to plan	$ 47,100	$ 2,000