GOODWILL AND INTANGIBLE ASSETS - Carrying Amount of Goodwill by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Dec. 28, 2019
Goodwill
Gross balance, beginning		$ 478,111
Accumulated impairment losses		(49,247)
Balance, ending	$ 428,864	428,864
Carrying amount of goodwill
Balance at the beginning of the period	428,864
Acquisitions	1,100
Foreign currency translation	(7,450)
Balance at the end of the period	422,514
Engineered Support Structures Segment
Goodwill
Gross balance, beginning		228,634
Accumulated impairment losses		(18,670)
Balance, ending	203,820	209,964
Carrying amount of goodwill
Balance at the beginning of the period	209,964
Acquisitions	0
Foreign currency translation	(6,144)
Balance at the end of the period	203,820
Utility Support Structures Segment
Goodwill
Gross balance, beginning		130,594
Accumulated impairment losses		(14,355)
Balance, ending	117,200	116,239
Carrying amount of goodwill
Balance at the beginning of the period	116,239
Acquisitions	1,100
Foreign currency translation	(139)
Balance at the end of the period	117,200
Coatings Segment
Goodwill
Gross balance, beginning		93,747
Accumulated impairment losses		(16,222)
Balance, ending	76,238	77,525
Carrying amount of goodwill
Balance at the beginning of the period	77,525
Acquisitions	0
Foreign currency translation	(1,287)
Balance at the end of the period	76,238
Irrigation Segment
Goodwill
Gross balance, beginning		25,136
Accumulated impairment losses		0
Balance, ending	25,256	$ 25,136
Carrying amount of goodwill
Balance at the beginning of the period	25,136
Acquisitions	0
Foreign currency translation	120
Balance at the end of the period	$ 25,256