GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2023 USD ($)	Dec. 25, 2021 USD ($)	Dec. 30, 2023 USD ($)	Sep. 02, 2023 item	Dec. 31, 2022 USD ($)
Indefinite-lived Intangible Assets
Goodwill impairments		$ 47,467			$ 47,467
Number Of Reporting Units Impaired for Goodwill | item				2
Goodwill impairment			$ 121,915
Valmont SM
Indefinite-lived Intangible Assets
Impairment of intangible assets		$ 2,013
Impairment, Intangible Asset, Indefinite-Lived (Excluding Goodwill), Statement of Income or Comprehensive Income [Extensible Enumeration]		Impairment Of Goodwill And Intangible Assets, Within Selling, General, And Administrative Expenses
Customer relationships
Indefinite-lived Intangible Assets
Impairment charge for intangible assets		$ 4,483
Impairment, Intangible Asset, Finite-Lived, Statement of Income or Comprehensive Income [Extensible Enumeration]		Impairment Of Goodwill And Intangible Assets, Within Selling, General, And Administrative Expenses
Agriculture
Indefinite-lived Intangible Assets
Goodwill impairment	$ 120,000		120,000
Agriculture | Proprietary technology intangible asset related to Prospera | Prospera
Indefinite-lived Intangible Assets
Impairment charge for intangible assets	$ 17,273
Impairment, Intangible Asset, Finite-Lived, Statement of Income or Comprehensive Income [Extensible Enumeration]	Impairment Of Goodwill And Intangible Assets, Within Selling, General, And Administrative Expenses
Infrastructure
Indefinite-lived Intangible Assets
Goodwill impairments		$ 47,467			$ 47,467
Goodwill impairment	$ 1,915		1,915
Infrastructure | Trade names
Indefinite-lived Intangible Assets
Impairment of intangible assets			$ 1,656
Impairment, Intangible Asset, Indefinite-Lived (Excluding Goodwill), Statement of Income or Comprehensive Income [Extensible Enumeration]			Impairment Of Goodwill And Intangible Assets, Within Selling, General, And Administrative Expenses