EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 27, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 26, 2015	Dec. 27, 2014	Dec. 28, 2013
Basic EPS
Net earnings attributable to Valmont Industries, Inc.	$ (30,561,000)	$ 12,066,000	$ 27,873,000	$ 30,739,000	$ 40,461,000	$ 23,559,000	$ 63,976,000	$ 55,980,000	$ 40,117,000	$ 183,976,000	$ 278,489,000
Shares outstanding basic (in shares)									23,288	25,719	26,641
Per share amount basic (in dollars per share)	$ (1.34)	$ 0.52	$ 1.19	$ 1.29	$ 1.67	$ 0.93	$ 2.40	$ 2.10	$ 1.72	$ 7.15	$ 10.45
Dilutive Effect of Stock Options
Dilutive Effect of Stock Options									$ 0	$ 0	$ 0
Dilutive effect of stock options number of shares (in shares)									117	213	258
Dilutive effect of stock options (in dollars per share)									$ 0.01	$ 0.06	$ 0.10
Diluted EPS
Diluted EPS									$ 40,117,000	$ 183,976,000	$ 278,489,000
Shares outstanding dilutive (in shares)									23,405	25,932	26,899
Per share amount diluted (in dollars per share)	$ (1.34)	$ 0.52	$ 1.19	$ 1.28	$ 1.66	$ 0.92	$ 2.38	$ 2.08	$ 1.71	$ 7.09	$ 10.35