EARNINGS (LOSS) PER SHARE - Reconciliation of earnings (loss) and share amounts to compute basic and diluted earnings (loss) per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 24, 2022	Sep. 30, 2023	Sep. 24, 2022
Earnings Per Share [Abstract]
Net earnings (loss) attributable to Valmont Industries, Inc.	$ (49,028)	$ 72,112	$ 114,888	$ 210,531
Weighted average shares outstanding:
Basic (in shares)	20,951	21,332	21,083	21,308
Dilutive effect of various stock awards (in shares)		273	207	238
Diluted (in shares)	20,951	21,605	21,290	21,546
Earnings (loss) per share:
Basic (in dollars per share)	$ (2.34)	$ 3.38	$ 5.45	$ 9.88
Dilutive effect of various stock awards (in dollars per share)		(0.04)	(0.05)	(0.11)
Diluted (in dollars per share)	$ (2.34)	$ 3.34	$ 5.40	$ 9.77