GOODWILL AND INTANGIBLE ASSETS - Carrying Amount of Goodwill by Segment (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 25, 2016	Jun. 25, 2016	Dec. 26, 2015
Goodwill
Goodwill, Gross			$ 371,808
Carrying amount of goodwill
Balance at the beginning of the period		$ 336,916
Balance at December 26, 2015			(34,892)
Foreign currency translation		(5,313)
Balance at the end of the period	$ 331,603	331,603	336,916
Engineered Support Structures Segment
Goodwill
Goodwill, Gross			101,275
Carrying amount of goodwill
Balance at the beginning of the period		101,275
Foreign currency translation		(2,589)
Balance at the end of the period	98,686	98,686	101,275
Energy and Mining Segment
Goodwill
Goodwill, Gross			99,829
Carrying amount of goodwill
Balance at the beginning of the period		81,159
Balance at December 26, 2015			(18,670)
Foreign currency translation	(3,200)
Balance at the end of the period	77,959	77,959	81,159
Utility Support Structures Segment
Goodwill
Goodwill, Gross			75,404
Carrying amount of goodwill
Balance at the beginning of the period		75,404
Foreign currency translation		0
Balance at the end of the period	75,404	75,404	75,404
Coatings Segment
Goodwill
Goodwill, Gross			75,941
Carrying amount of goodwill
Balance at the beginning of the period		59,719
Balance at December 26, 2015	(9,100)		(16,222)
Foreign currency translation		411
Balance at the end of the period	60,130	60,130	59,719
Irrigation Segment
Goodwill
Goodwill, Gross			19,359
Carrying amount of goodwill
Balance at the beginning of the period		19,359
Foreign currency translation		65
Balance at the end of the period	$ 19,424	$ 19,424	$ 19,359