GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	$ 122,319	$ 178,391	$ 45,333
Foreign currency translation adjustments:
Unrealized translation gains (losses)	79,279	(58,315)	(96,694)
Foreign currency translation adjustment		(58,315)	(96,694)
Unrealized gain/(loss) on cash flow hedge:
Unrealized gain (loss) on net investment hedge	(1,695)	4,226	0
Amortization cost included in interest expense	74	74	74
Realized (gain) loss included in net earnings	0	0	(3,130)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	0	0	2,855
Derivative adjustment	(1,621)	4,300	(201)
Actuarial gain (loss) in defined benefit pension plan	(10,871)	(24,141)	(40,274)
Equity in other comprehensive income	0	0	0
Other comprehensive income (loss)	66,787	(78,156)	(137,169)
Comprehensive income (loss)	189,106	100,235	(91,836)
Comprehensive loss (income) attributable to noncontrolling interests	(5,529)	(6,144)	(832)
Comprehensive income (loss) attributable to Valmont Industries, Inc.	183,577	94,091	(92,668)
Eliminations
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	(105,852)	(208,027)	27,217
Foreign currency translation adjustments:
Unrealized translation gains (losses)	0	0	0
Foreign currency translation adjustment		0	0
Unrealized gain/(loss) on cash flow hedge:
Unrealized gain (loss) on net investment hedge	0	0
Amortization cost included in interest expense	0	0	0
Realized (gain) loss included in net earnings			0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			0
Derivative adjustment	0	0	0
Actuarial gain (loss) in defined benefit pension plan	0	0	0
Equity in other comprehensive income	(68,958)	83,252	132,584
Other comprehensive income (loss)	(68,958)	83,252	132,584
Comprehensive income (loss)	(174,810)	(124,775)	159,801
Comprehensive loss (income) attributable to noncontrolling interests	0	0	0
Comprehensive income (loss) attributable to Valmont Industries, Inc.	(174,810)	(124,775)	159,801
Parent
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	116,240	173,232	40,117
Foreign currency translation adjustments:
Unrealized translation gains (losses)	0	0	0
Foreign currency translation adjustment		0	0
Unrealized gain/(loss) on cash flow hedge:
Unrealized gain (loss) on net investment hedge	(1,695)	4,226
Amortization cost included in interest expense	74	74	74
Realized (gain) loss included in net earnings			(3,130)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			2,855
Derivative adjustment	(1,621)	4,300	(201)
Actuarial gain (loss) in defined benefit pension plan	0	0	0
Equity in other comprehensive income	68,958	(83,252)	(132,584)
Other comprehensive income (loss)	67,337	(78,952)	(132,785)
Comprehensive income (loss)	183,577	94,280	(92,668)
Comprehensive loss (income) attributable to noncontrolling interests	0	0	0
Comprehensive income (loss) attributable to Valmont Industries, Inc.	183,577	94,280	(92,668)
Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	52,562	104,625	(10,760)
Foreign currency translation adjustments:
Unrealized translation gains (losses)	138,795	49	(15,166)
Foreign currency translation adjustment		49	(15,166)
Unrealized gain/(loss) on cash flow hedge:
Unrealized gain (loss) on net investment hedge	0	0
Amortization cost included in interest expense	0	0	0
Realized (gain) loss included in net earnings			0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			0
Derivative adjustment	0	0	0
Actuarial gain (loss) in defined benefit pension plan	0	0	0
Equity in other comprehensive income	0	0	0
Other comprehensive income (loss)	138,795	49	(15,166)
Comprehensive income (loss)	191,357	104,674	(25,926)
Comprehensive loss (income) attributable to noncontrolling interests	0	0	0
Comprehensive income (loss) attributable to Valmont Industries, Inc.	191,357	104,674	(25,926)
Non- Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net earnings	59,369	108,561	(11,241)
Foreign currency translation adjustments:
Unrealized translation gains (losses)	(59,516)	(58,364)	(81,528)
Foreign currency translation adjustment		(58,364)	(81,528)
Unrealized gain/(loss) on cash flow hedge:
Unrealized gain (loss) on net investment hedge	0	0
Amortization cost included in interest expense	0	0	0
Realized (gain) loss included in net earnings			0
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax			0
Derivative adjustment	0	0	0
Actuarial gain (loss) in defined benefit pension plan	(10,871)	(24,141)	(40,274)
Equity in other comprehensive income	0	0	0
Other comprehensive income (loss)	(70,387)	(82,505)	(121,802)
Comprehensive income (loss)	(11,018)	26,056	(133,043)
Comprehensive loss (income) attributable to noncontrolling interests	(5,529)	(6,144)	(832)
Comprehensive income (loss) attributable to Valmont Industries, Inc.	$ (16,547)	$ 19,912	$ (133,875)