EARNINGS PER SHARE - Reconciliation of earnings and share amounts to compute basic and diluted earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 29, 2025	Mar. 30, 2024
EARNINGS PER SHARE
Net earnings attributable to Valmont Industries, Inc.	$ 87,261	$ 87,822
Weighted average shares outstanding (in thousands):
Basic (in shares)	20,047	20,188
Dilutive effect of various stock awards (in shares)	149	133
Diluted (in shares)	20,196	20,321
Net earnings attributable to Valmont Industries, Inc. per share:
Basic (in dollars per share)	$ 4.35	$ 4.35
Dilutive effect of various stock awards (in dollars per share)	(0.03)	(0.03)
Diluted (in dollars per share)	$ 4.32	$ 4.32