EARNINGS PER SHARE (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Basic EPS
Net earnings attributable to Valmont Industries, Inc.	$ 41,397,000	$ 32,960,000	$ 77,878,000	$ 72,241,000
Weighted average shares outstanding (in shares)	21,734,000	22,438,000	21,810,000	22,523,000
Per share amount basic (in dollars per share)	$ 1.90	$ 1.47	$ 3.57	$ 3.21
Dilutive Effect of Stock Options
Dilutive Effect of Stock Options	$ 0	$ 0	$ 0	$ 0
Dilutive effect of stock options number of shares (in shares)	97,000	135,000	87,000	161,000
Dilutive effect of stock options (in dollars per share)	$ 0	$ (0.01)	$ (0.01)	$ (0.03)
Diluted EPS
Diluted EPS	$ 41,397,000	$ 32,960,000	$ 77,878,000	$ 72,241,000
Shares outstanding dilutive (in shares)	21,831,000	22,573,000	21,897,000	22,684,000
Per share amount diluted (in dollars per share)	$ 1.90	$ 1.46	$ 3.56	$ 3.18
Impact on net income (loss) available for common stockholders	$ (41,397,000)	$ (32,960,000)	$ (77,878,000)	$ (72,241,000)
Impact effect on earnings per share basic (in dollars per share)	$ (1.90)	$ (1.47)	$ (3.57)	$ (3.21)
Impact effect on net income (loss) available to common stockholders, diluted (in dollars per share)	$ (41,397,000)	$ (32,960,000)	$ (77,878,000)	$ (72,241,000)
Impact effect on earnings per share diluted (in dollars per share)	$ (1.90)	$ (1.46)	$ (3.56)	$ (3.18)
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)			297,170	145,105