EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 30, 2019	Mar. 31, 2018
Basic EPS
Net earnings attributable to Valmont Industries, Inc.	$ 36,481	$ 39,281
Weighted average shares outstanding (in shares)	21,886,000	22,609,000
Per share amount basic (in dollars per share)	$ 1.67	$ 1.74
Dilutive Effect of Stock Options
Dilutive Effect of Stock Options	$ 0	$ 0
Dilutive effect of stock options number of shares (in shares)	78,000	187,000
Dilutive effect of stock options (in dollars per share)	$ 0.01	$ 0.02
Diluted EPS
Diluted EPS	$ 36,481	$ 39,281
Shares outstanding dilutive (in shares)	21,964,000	22,796,000
Per share amount diluted (in dollars per share)	$ 1.66	$ 1.72
Impact on net income (loss) available for common stockholders	$ (36,481)	$ (39,281)
Impact effect on earnings per share basic (in dollars per share)	$ (1.67)	$ (1.74)
Impact effect on net income (loss) available to common stockholders, diluted (in dollars per share)	$ (36,481)	$ (39,281)
Impact effect on earnings per share diluted (in dollars per share)	$ (1.66)	$ (1.72)
Antidilutive Securities
Outstanding stock options with exercise prices exceeding the market price of common stock, excluded from the computation of diluted earnings per share (in shares)	297,412	147,554