EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Basic EPS
Net earnings attributable to Valmont Industries, Inc.	$ 70,064,000	$ 28,173,000	$ 42,026,000	$ 32,969,000	$ (30,561,000)	$ 12,066,000	$ 27,873,000	$ 30,739,000	$ 173,232,000	$ 40,117,000	$ 183,976,000
Shares outstanding basic (in shares)									22,562	23,288	25,719
Per share amount basic (in dollars per share)	$ 3.12	$ 1.25	$ 1.86	$ 1.45	$ (1.34)	$ 0.52	$ 1.19	$ 1.29	$ 7.68	$ 1.72	$ 7.15
Dilutive Effect of Stock Options
Dilutive Effect of Stock Options									$ 0	$ 0	$ 0
Dilutive effect of stock options number of shares (in shares)									147	117	213
Dilutive effect of stock options (in dollars per share)									$ 0.05	$ 0.01	$ 0.06
Diluted EPS
Diluted EPS									$ 173,232,000	$ 40,117,000	$ 183,976,000
Shares outstanding dilutive (in shares)									22,709	23,405	25,932
Per share amount diluted (in dollars per share)	$ 3.10	$ 1.24	$ 1.85	$ 1.45	$ (1.34)	$ 0.52	$ 1.19	$ 1.28	$ 7.63	$ 1.71	$ 7.09