EARNINGS PER SHARE (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015
Basic EPS
Net earnings attributable to Valmont Industries, Inc.	$ 28,173,000	$ 12,066,000	$ 103,168,000	$ 70,678,000
Shares outstanding basic (in shares)	22,505,000	23,057,000	22,602,000	23,420,000
Per share amount basic (in dollars per share)	$ 1.25	$ 0.52	$ 4.56	$ 3.02
Dilutive Effect of Stock Options
Dilutive Effect of Stock Options	$ 0	$ 0	$ 0	$ 0
Dilutive effect of stock options number of shares (in shares)	154,000	113,000	139,000	114,000
Dilutive effect of stock options (in dollars per share)	$ (0.01)	$ 0.00	$ (0.02)	$ (0.02)
Diluted EPS
Diluted EPS	$ 28,173,000	$ 12,066,000	$ 103,168,000	$ 70,678,000
Shares outstanding dilutive (in shares)	22,659,000	23,170,000	22,741,000	23,534,000
Per share amount diluted (in dollars per share)	$ 1.24	$ 0.52	$ 4.54	$ 3.00
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	433,401