EARNINGS (LOSS) 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		6 Months Ended
	Jun. 28, 2025	Jun. 29, 2024	Jun. 28, 2025	Jun. 29, 2024
EARNINGS (LOSS) PER SHARE
Net earnings (loss) attributable to Valmont Industries, Inc.	$ (4,020)	$ 99,716	$ 83,241	$ 187,538
Change in redemption value of redeemable noncontrolling interest	(26,243)		(26,243)
Net earnings (loss) attributable to Valmont Industries, Inc. including change in redemption value of redeemable noncontrolling interests	$ (30,263)	$ 99,716	$ 56,998	$ 187,538
Weighted average shares outstanding (in thousands):
Basic (in shares)	19,809	20,175	19,928	20,182
Dilutive effect of various stock awards (in shares)		117	135	125
Diluted (in shares)	19,809	20,292	20,063	20,307
Net earnings (loss) attributable to Valmont Industries, Inc. per share:
Basic (in dollars per share)	$ (1.53)	$ 4.94	$ 2.86	$ 9.29
Dilutive effect of various stock awards (in dollars per share)		(0.03)	(0.02)	(0.05)
Diluted (in dollars per share)	$ (1.53)	$ 4.91	$ 2.84	$ 9.24