GOODWILL AND INTANGIBLE ASSETS - Carrying Amount of Goodwill by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 27, 2021	Dec. 26, 2020
Goodwill
Gross balance, beginning		$ 492,144
Accumulated impairment losses		(61,822)
Balance, ending	$ 429,927	430,322
Carrying amount of goodwill
Balance at the beginning of the period	430,322
Foreign currency translation	(395)
Balance at the end of the period	429,927
Engineered Support Structures Segment
Goodwill
Gross balance, beginning		232,323
Accumulated impairment losses		(31,245)
Balance, ending	202,282	201,078
Carrying amount of goodwill
Balance at the beginning of the period	201,078
Foreign currency translation	1,204
Balance at the end of the period	202,282
Utility Support Structures Segment
Goodwill
Gross balance, beginning		135,335
Accumulated impairment losses		(14,355)
Balance, ending	119,542	120,980
Carrying amount of goodwill
Balance at the beginning of the period	120,980
Foreign currency translation	(1,438)
Balance at the end of the period	119,542
Coatings Segment
Goodwill
Gross balance, beginning		94,309
Accumulated impairment losses		(16,222)
Balance, ending	78,294	78,087
Carrying amount of goodwill
Balance at the beginning of the period	78,087
Foreign currency translation	207
Balance at the end of the period	78,294
Irrigation Segment
Goodwill
Gross balance, beginning		30,177
Accumulated impairment losses		0
Balance, ending	29,809	$ 30,177
Carrying amount of goodwill
Balance at the beginning of the period	30,177
Foreign currency translation	(368)
Balance at the end of the period	$ 29,809