CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Statement of Comprehensive Income [Abstract]
Net earnings	$ 142,149	$ 152,105	$ 107,725
Foreign currency translation adjustments:
Unrealized translation gains (losses)	21,483	(2,506)	(65,436)
Realized loss on divestiture of grinding media business recorded in other expense	0	0	9,203
Foreign currency translation adjustments	21,483	(2,506)	(56,233)
Gain/(loss) on hedging activities:
Unrealized gain on net investment hedges, net of tax expense (benefit) of $2,428 in 2020, $384 in 2019, $1,894 in 2018	7,289	1,154	5,291
Realized loss on grinding media net investment hedge	0	0	1,215
Amortization cost (benefit) included in interest expense	(64)	(64)	423
Deferred loss on interest rate hedges	0	0	(2,467)
Cash flow hedges	1,598	0	0
Realized (gain) loss on cash flow hedges recorded in earnings	(1,598)	0	0
Commodity hedges	0	(2,130)	1,021
Realized (gain) loss on commodity hedges recorded in earnings	0	2,130	(1,021)
Unrealized gain (loss) on cross currency swaps	(5,751)	1,815	352
Other Comprehensive Income Loss, Hedging Activities, Gain (loss), after Reclassification and Tax	1,474	2,905	4,814
Actuarial gain (loss) on defined benefit pension plan, net of tax expense (benefit) of $(4,183) in 2020, $(2,710) in 2019, $8,177 in 2018	(17,349)	(10,828)	29,885
Other comprehensive income (loss)	5,608	(10,429)	(21,534)
Comprehensive income	147,757	141,676	86,191
Comprehensive income attributable to noncontrolling interests	(3,428)	(5,505)	(8,584)
Comprehensive income attributable to Valmont Industries, Inc.	$ 144,329	$ 136,171	$ 77,607