CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Statement of Comprehensive Income [Abstract]
Net earnings	$ 34,680	$ 47,322	$ 75,160	$ 87,283
Foreign currency translation adjustments:
Unrealized translation gain (loss)	(46,953)	21,551	(40,149)	40,941
Realized loss on divestiture of grinding media business recorded in earnings	9,203	0	9,203	0
Gain (loss) on hedging activities:
Net investment hedges	2,396	(550)	1,607	(1,076)
Realized loss on net investment hedge for grinding media business recorded in earnings	1,215	0	1,215	0
Amortization cost included in interest expense	25	18	44	37
Loss (deferred) on interest rate hedges	(2,467)	0	(2,467)	0
Commodity hedges	1,438	0	1,345	0
Other comprehensive income (loss)	(35,143)	21,019	(29,202)	39,902
Comprehensive income	(463)	68,341	45,958	127,185
Comprehensive loss (income) attributable to noncontrolling interests	(1,114)	(2,223)	(5,861)	(1,982)
Comprehensive income attributable to Valmont Industries, Inc.	$ (1,577)	$ 66,118	$ 40,097	$ 125,203