EARNINGS PER SHARE (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 29, 2012	Sep. 29, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 24, 2011	Jun. 25, 2011	Mar. 26, 2011	Dec. 29, 2012	Dec. 31, 2011	Dec. 25, 2010
Basic EPS
Net earnings attributable to Valmont Industries, Inc, basic	$ 65,036	$ 56,731	$ 59,980	$ 52,325	$ 114,731	$ 42,141	$ 45,827	$ 25,609	$ 234,072	$ 228,308	$ 94,379
Shares outstanding basic									26,471	26,329	26,100
Per share amount basic (in dollars per share)	$ 2.45	$ 2.14	$ 2.27	$ 1.98	$ 4.35	$ 1.60	$ 1.74	$ 0.98	$ 8.84	$ 8.67	$ 3.62
Dilutive Effect of Stock Options
Dilutive effect of stock options number of shares									293	221	322
Dilutive effect of stock options (in dollars per share)									$ 0.09	$ 0.07	$ 0.05
Diluted EPS
Net earnings attributable to Valmont Industries, Inc, diluted									$ 234,072	$ 228,308	$ 94,379
Shares outstanding dilutive									26,764	26,550	26,422
Per share amount diluted (in dollars per share)	$ 2.43	$ 2.12	$ 2.24	$ 1.96	$ 4.33	$ 1.59	$ 1.72	$ 0.97	$ 8.75	$ 8.60	$ 3.57
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)									137,000	20,000	8,000