GOODWILL AND INTANGIBLE ASSETS (Details 4) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Jun. 25, 2016	Dec. 26, 2015	Dec. 31, 2016	Dec. 26, 2015
Goodwill [Line Items]
Goodwill, Gross		$ 371,808		$ 371,808
Carrying amount of goodwill
Balance at the beginning of the period			$ 336,916	385,111
Accumulated impairment losses		(7,100)		(34,892)
Acquisition				3,019
Foreign currency translation			(15,806)	(14,585)
Divestiture of business				1,737
Balance at the end of the period		336,916	321,110	336,916
Engineered Support Structures
Goodwill [Line Items]
Goodwill, Gross		101,275		101,275
Carrying amount of goodwill
Balance at the beginning of the period			101,275	107,868
Accumulated impairment losses				0
Acquisition				0
Foreign currency translation			(6,961)	(4,856)
Divestiture of business	$ (1,737)			1,737
Balance at the end of the period		101,275	94,314	101,275
Energy and Mining Segment
Goodwill [Line Items]
Goodwill, Gross		99,829		99,829
Carrying amount of goodwill
Balance at the beginning of the period			81,159	106,770
Accumulated impairment losses		(19,000)		(18,670)
Acquisition				0
Foreign currency translation			(8,947)	(6,941)
Divestiture of business				0
Balance at the end of the period		81,159	72,212	81,159
Utility Support Structures Segment
Goodwill [Line Items]
Goodwill, Gross		75,404		75,404
Carrying amount of goodwill
Balance at the beginning of the period			75,404	75,404
Accumulated impairment losses				0
Acquisition				0
Foreign currency translation			0	0
Divestiture of business				0
Balance at the end of the period		75,404	75,404	75,404
Coatings Segment
Goodwill [Line Items]
Goodwill, Gross		75,941		75,941
Carrying amount of goodwill
Balance at the beginning of the period			59,719	75,533
Accumulated impairment losses				(16,222)
Acquisition				3,019
Foreign currency translation			(150)	(2,611)
Divestiture of business				0
Balance at the end of the period		59,719	59,569	59,719
Irrigation Segment
Goodwill [Line Items]
Goodwill, Gross		19,359		19,359
Carrying amount of goodwill
Balance at the beginning of the period			19,359	19,536
Accumulated impairment losses				0
Acquisition				0
Foreign currency translation			252	(177)
Divestiture of business				0
Balance at the end of the period		$ 19,359	$ 19,611	$ 19,359