GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION - Condensed Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Apr. 01, 2017
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings		$ 40,480	$ 39,961
Foreign currency translation adjustments:
Unrealized translation gain		6,804	19,390
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax			(526)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		(93)	0
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)	$ (792)	(789)	(526)
Gain/(loss) on hedging activities:
Amortization cost included in interest expense		19	19
Equity in other comprehensive income		0	0
Other comprehensive income (loss)		5,941	18,883
Comprehensive income		46,421	58,844
Comprehensive loss (income) attributable to noncontrolling interests		(4,747)	241
Comprehensive income attributable to Valmont Industries, Inc.		41,674	59,085
Consolidation, Eliminations [Member]
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings		(25,741)	(27,986)
Foreign currency translation adjustments:
Unrealized translation gain		0	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax			0
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
Equity in other comprehensive income		(3,256)	(20,613)
Other comprehensive income (loss)		(3,256)	(20,613)
Comprehensive income		(28,997)	(48,599)
Comprehensive loss (income) attributable to noncontrolling interests		0	0
Comprehensive income attributable to Valmont Industries, Inc.		(28,997)	(48,599)
Parent
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings		39,281	38,979
Foreign currency translation adjustments:
Unrealized translation gain		0	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax			(526)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		(93)
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)		(789)
Gain/(loss) on hedging activities:
Amortization cost included in interest expense		19	19
Equity in other comprehensive income		3,256	20,613
Other comprehensive income (loss)		2,393	20,106
Comprehensive income		41,674	59,085
Comprehensive loss (income) attributable to noncontrolling interests		0	0
Comprehensive income attributable to Valmont Industries, Inc.		41,674	59,085
Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings		10,989	5,540
Foreign currency translation adjustments:
Unrealized translation gain		(8,680)	69,383
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax			0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		0
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
Equity in other comprehensive income		0	0
Other comprehensive income (loss)		(8,680)	69,383
Comprehensive income		2,309	74,923
Comprehensive loss (income) attributable to noncontrolling interests		0	0
Comprehensive income attributable to Valmont Industries, Inc.		2,309	74,923
Non- Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings		15,951	23,428
Foreign currency translation adjustments:
Unrealized translation gain		15,484	(49,993)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax			0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		0
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
Equity in other comprehensive income		0	0
Other comprehensive income (loss)		15,484	(49,993)
Comprehensive income		31,435	(26,565)
Comprehensive loss (income) attributable to noncontrolling interests		(4,747)	241
Comprehensive income attributable to Valmont Industries, Inc.		26,688	$ (26,324)
Consolidation, Eliminations [Member]
Foreign currency translation adjustments:
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		$ 0