EARNINGS PER SHARE (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 24, 2016	Sep. 30, 2017	Sep. 24, 2016
Basic EPS
Net earnings attributable to Valmont Industries, Inc.	$ 35,208,000	$ 28,173,000	$ 119,851,000	$ 103,168,000
Shares outstanding basic (in shares)	22,527,000	22,505,000	22,505,000	22,602,000
Per share amount basic (in dollars per share)	$ 1.56	$ 1.25	$ 5.33	$ 4.56
Dilutive Effect of Stock Options
Dilutive Effect of Stock Options	$ 0	$ 0	$ 0	$ 0
Dilutive effect of stock options number of shares (in shares)	224,000	154,000	212,000	139,000
Dilutive effect of stock options (in dollars per share)	$ (0.01)	$ (0.01)	$ (0.05)	$ (0.02)
Diluted EPS
Diluted EPS	$ 35,208,000	$ 28,173,000	$ 119,851,000	$ 103,168,000
Shares outstanding dilutive (in shares)	22,751,000	22,659,000	22,717,000	22,741,000
Per share amount diluted (in dollars per share)	$ 1.55	$ 1.24	$ 5.28	$ 4.54
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)				378,566