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GOODWILL AND INTANGIBLE ASSETS (Details 4) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 29, 2018	Dec. 28, 2019	Dec. 29, 2018	Sep. 28, 2019	Dec. 30, 2017
Indefinite-lived Intangible Assets
Goodwill		$ 428,864	$ 385,207		$ 337,720
Hypothetical change in discount rate		1.00%
Effect of change in discount rate on fair value of reporting unit		$ 15,000
Goodwill impairment	$ 14,355		$ 14,355
Access Systems
Indefinite-lived Intangible Assets
Goodwill				$ 45,727
Valmont SM
Indefinite-lived Intangible Assets
Impairment of intangible assets	$ 1,425