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	12 Months Ended
	Dec. 28, 2024	Dec. 30, 2023	Dec. 31, 2022
EARNINGS PER SHARE
Net Income (Loss)	$ 348,259	$ 150,849	$ 250,863
Change in redemption value of redeemable noncontrolling interest		(7,374)
Net earnings (loss) attributable to Valmont Industries, Inc.	$ 348,259	$ 143,475	$ 250,863
Weighted average shares outstanding (in thousands):
Basic (in shares)	20,122	20,956	21,311
Dilutive effect of various stock awards (in shares)	139	203	269
Diluted (in shares)	20,261	21,159	21,580
Net earnings attributable to Valmont Industries, Inc. per share:
Basic (in dollars per share)	$ 17.31	$ 6.85	$ 11.77
Dilutive effect of various stock awards (in dollars per share)	(0.12)	(0.07)	(0.15)
Diluted (in dollars per share)	$ 17.19	$ 6.78	$ 11.62