SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Long-lived assets
Depreciation expense	$ 69,046	$ 66,482	$ 72,805
Impairment of Melbourne Galvanizing site's equipment			$ 4,151
Buildings and improvements | Minimum
Long-lived assets
Estimated useful lives	15 years
Buildings and improvements | Maximum
Long-lived assets
Estimated useful lives	40 years
Machinery and equipment | Minimum
Long-lived assets
Estimated useful lives	3 years
Machinery and equipment | Maximum
Long-lived assets
Estimated useful lives	12 years
Transportation equipment | Minimum
Long-lived assets
Estimated useful lives	3 years
Transportation equipment | Maximum
Long-lived assets
Estimated useful lives	24 years
Office furniture and equipment | Minimum
Long-lived assets
Estimated useful lives	3 years
Office furniture and equipment | Maximum
Long-lived assets
Estimated useful lives	7 years