EARNINGS PER SHARE - Reconciliation of earnings and share amounts to compute basic and diluted earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2023	Jun. 25, 2022	Jul. 01, 2023	Jun. 25, 2022
Earnings Per Share [Abstract]
Net earnings attributable to Valmont Industries, Inc.	$ 89,376	$ 76,108	$ 163,916	$ 138,419
Weighted average shares outstanding:
Basic weighted average shares outstanding	21,029	21,313	21,149	21,296
Dilutive effect of various stock awards	200	228	221	220
Diluted weighted average shares outstanding	21,229	21,541	21,370	21,516
Earnings per share:
Basic	$ 4.25	$ 3.57	$ 7.75	$ 6.50
Dilutive effect of various stock awards	(0.04)	(0.04)	(0.08)	(0.07)
Diluted	$ 4.21	$ 3.53	$ 7.67	$ 6.43