GOODWILL AND INTANGIBLE ASSETS (Details 4) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 29, 2018	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill, Gross			$ 372,612	$ 356,002
Goodwill, Impaired, Accumulated Impairment Loss			(34,892)
Carrying amount of goodwill
Balance at the beginning of the period		$ 337,720	321,110
Acquisitions	$ (14,355)	(14,355)	(34,892)
Goodwill, Transfers		(15,814)
Acquisition		87,119	3,449
Foreign currency translation		(9,463)	13,161
Balance at the end of the period		385,207	337,720
Engineered Support Structures
Goodwill [Line Items]
Goodwill, Gross			170,076	157,689
Goodwill, Impaired, Accumulated Impairment Loss			(18,670)
Carrying amount of goodwill
Balance at the beginning of the period		151,406	139,019
Acquisitions		0	(18,670)
Goodwill, Transfers		0
Acquisition		42,216	3,449
Foreign currency translation			8,938
Balance at the end of the period		186,065	151,406
Coatings Segment
Goodwill [Line Items]
Goodwill, Gross			90,248	88,451
Goodwill, Impaired, Accumulated Impairment Loss			0
Carrying amount of goodwill
Balance at the beginning of the period		90,248	88,451
Acquisitions		(14,355)	0
Goodwill, Transfers		0
Acquisition		34,280	0
Foreign currency translation			1,797
Balance at the end of the period		109,263	90,248
Irrigation Segment
Goodwill [Line Items]
Goodwill, Gross			76,696	75,791
Goodwill, Impaired, Accumulated Impairment Loss			(16,222)
Carrying amount of goodwill
Balance at the beginning of the period		60,474	59,569
Acquisitions		0	(16,222)
Goodwill, Transfers		0
Acquisition		5,120	0
Foreign currency translation			905
Balance at the end of the period		64,715	60,474
Other
Goodwill [Line Items]
Goodwill, Gross			19,778	19,611
Goodwill, Impaired, Accumulated Impairment Loss			0
Carrying amount of goodwill
Balance at the beginning of the period		19,778	19,611
Acquisitions		0	0
Goodwill, Transfers		0
Acquisition		5,503	0
Foreign currency translation			167
Balance at the end of the period		25,164	19,778
Other
Goodwill [Line Items]
Goodwill, Gross			15,814	$ 14,460
Goodwill, Impaired, Accumulated Impairment Loss			0
Carrying amount of goodwill
Balance at the beginning of the period		15,814	14,460
Acquisitions		0	0
Goodwill, Transfers		(15,814)
Acquisition		0	0
Foreign currency translation			1,354
Balance at the end of the period		$ 0	$ 15,814