GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION - Condensed Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jun. 25, 2016	Jul. 01, 2017	Jun. 25, 2016
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	$ 47,322	$ 43,442	$ 87,283	$ 77,613
Foreign currency translation adjustments:
Unrealized translation gain (loss)	21,551	(2,296)	40,941	217
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)	(550)	0	(1,076)	0
Gain/(loss) on hedging activities:
Amortization cost included in interest expense	18	19	37	38
Equity in other comprehensive income	0	0	0	0
Other comprehensive income (loss)	21,019	(2,277)	39,902	255
Comprehensive income	68,341	41,165	127,185	77,868
Comprehensive loss (income) attributable to noncontrolling interests	(2,223)	(1,787)	(1,982)	(4,114)
Comprehensive income attributable to Valmont Industries, Inc.	66,118	39,378	125,203	73,754
Eliminations
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	(34,569)	(35,996)	(62,555)	(56,108)
Foreign currency translation adjustments:
Unrealized translation gain (loss)	0	0	0	0
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)	0		0
Gain/(loss) on hedging activities:
Amortization cost included in interest expense	0	0	0	0
Equity in other comprehensive income	(20,986)	5,592	(41,599)	1,279
Other comprehensive income (loss)	(20,986)	5,592	(41,599)	1,279
Comprehensive income	(55,555)	(30,404)	(104,154)	(54,829)
Comprehensive loss (income) attributable to noncontrolling interests	0	0	0	0
Comprehensive income attributable to Valmont Industries, Inc.	(55,555)	(30,404)	(104,154)	(54,829)
Parent
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	45,664	42,026	84,643	74,995
Foreign currency translation adjustments:
Unrealized translation gain (loss)	0	2,925	0	2,925
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)	(550)		(1,076)
Gain/(loss) on hedging activities:
Amortization cost included in interest expense	18	19	37	38
Equity in other comprehensive income	20,986	(5,592)	41,599	(1,279)
Other comprehensive income (loss)	20,454	(2,648)	40,560	1,684
Comprehensive income	66,118	39,378	125,203	76,679
Comprehensive loss (income) attributable to noncontrolling interests	0	0	0	0
Comprehensive income attributable to Valmont Industries, Inc.	66,118	39,378	125,203	76,679
Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	16,890	16,524	22,430	26,187
Foreign currency translation adjustments:
Unrealized translation gain (loss)	(1,359)	29	68,024	(149)
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)	0
Gain/(loss) on hedging activities:
Amortization cost included in interest expense	0	0	0	0
Equity in other comprehensive income	0	0	0	0
Other comprehensive income (loss)	(1,359)	29	68,024	(149)
Comprehensive income	15,531	16,553	90,454	26,038
Comprehensive loss (income) attributable to noncontrolling interests	0	0	0	0
Comprehensive income attributable to Valmont Industries, Inc.	15,531	16,553	90,454	26,038
Non- Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	19,337	20,888	42,765	32,539
Foreign currency translation adjustments:
Unrealized translation gain (loss)	22,910	(5,250)	(27,083)	(2,559)
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)	0		0
Gain/(loss) on hedging activities:
Amortization cost included in interest expense	0	0	0	0
Equity in other comprehensive income	0	0	0	0
Other comprehensive income (loss)	22,910	(5,250)	(27,083)	(2,559)
Comprehensive income	42,247	15,638	15,682	29,980
Comprehensive loss (income) attributable to noncontrolling interests	(2,223)	(1,787)	(1,982)	(4,114)
Comprehensive income attributable to Valmont Industries, Inc.	$ 40,024	$ 13,851	$ 13,700	$ 25,866