GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION
Parent company's percentage ownership of Guarantors	100.00%								100.00%
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales	$ 674,575	$ 610,247	$ 640,249	$ 596,605	$ 633,828	$ 632,575	$ 682,123	$ 670,398	$ 2,521,676	$ 2,618,924	$ 3,123,143
Cost of sales									1,865,433	1,997,891	2,315,026
Gross profit	165,135	155,023	175,117	160,968	129,280	156,751	169,548	165,454	656,243	621,033	808,117
Selling, general and administrative expenses									412,739	447,368	450,401
Impairment of goodwill and intangible assets						13,400			0	41,970	0
Operating income									243,504	131,695	357,716
Other income (expense):
Interest expense									(44,409)	(44,621)	(36,790)
Interest income									3,105	3,296	6,046
Costs associated with refinancing of debt									0	0	(38,705)
Other									18,254	2,637	(4,084)
Total other income (expenses)									(23,050)	(38,688)	(73,533)
Earnings before income taxes and equity in earnings of nonconsolidated subsidiaries									220,454	93,007	284,183
Income tax expense (benefit):
Current									65,748	42,569	89,643
Deferred income taxes									(23,685)	4,858	5,251
Total income tax expense (benefit)									42,063	47,427	94,894
Earnings before equity in earnings of nonconsolidated subsidiaries									178,391	45,580	189,289
Equity in earnings of nonconsolidated subsidiaries									0	(247)	29
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax									13,652	0	0
Net earnings									178,391	45,333	189,318
Less: Earnings attributable to noncontrolling interests									(5,159)	(5,216)	(5,342)
Net earnings attributable to Valmont Industries, Inc.	$ 70,064	$ 28,173	$ 42,026	$ 32,969	$ (30,561)	$ 12,066	$ 27,873	$ 30,739	173,232	40,117	183,976
Eliminations
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales									(191,877)	(213,287)	(221,745)
Cost of sales									(190,716)	(212,927)	(222,234)
Gross profit									(1,161)	(360)	489
Selling, general and administrative expenses									0	0	0
Impairment of goodwill and intangible assets									0	0
Operating income									(1,161)	(360)	489
Other income (expense):
Interest expense									0	0	0
Interest income									0	0	0
Costs associated with refinancing of debt											0
Other									0	0	0
Total other income (expenses)									0	0	0
Earnings before income taxes and equity in earnings of nonconsolidated subsidiaries									(1,161)	(360)	489
Income tax expense (benefit):
Current									(323)	(1)	138
Deferred income taxes									0	0	0
Total income tax expense (benefit)									(323)	(1)	138
Earnings before equity in earnings of nonconsolidated subsidiaries									(838)	(359)	351
Equity in earnings of nonconsolidated subsidiaries									(207,189)	27,576	(148,574)
Net earnings									(208,027)	27,217	(148,223)
Less: Earnings attributable to noncontrolling interests									0	0	0
Net earnings attributable to Valmont Industries, Inc.									(208,027)	27,217	(148,223)
Parent
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales									1,126,985	1,169,674	1,392,509
Cost of sales									837,616	890,242	1,040,808
Gross profit									289,369	279,432	351,701
Selling, general and administrative expenses									184,493	194,335	196,987
Impairment of goodwill and intangible assets									0	0
Operating income									104,876	85,097	154,714
Other income (expense):
Interest expense									(43,703)	(43,552)	(34,267)
Interest income									273	9	38
Costs associated with refinancing of debt											(38,705)
Other									1,480	(2,374)	2,021
Total other income (expenses)									(41,950)	(45,917)	(70,913)
Earnings before income taxes and equity in earnings of nonconsolidated subsidiaries									62,926	39,180	83,801
Income tax expense (benefit):
Current									24,539	863	30,330
Deferred income taxes									6,216	10,042	(1,474)
Total income tax expense (benefit)									30,755	10,905	28,856
Earnings before equity in earnings of nonconsolidated subsidiaries									32,171	28,275	54,945
Equity in earnings of nonconsolidated subsidiaries									141,061	11,842	129,031
Net earnings									173,232	40,117	183,976
Less: Earnings attributable to noncontrolling interests									0	0	0
Net earnings attributable to Valmont Industries, Inc.									173,232	40,117	183,976
Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales									390,756	423,928	496,326
Cost of sales									285,924	332,847	371,639
Gross profit									104,832	91,081	124,687
Selling, general and administrative expenses									46,244	45,549	49,171
Impairment of goodwill and intangible assets									0	0
Operating income									58,588	45,532	75,516
Other income (expense):
Interest expense									(10)	0	(5)
Interest income									112	103	359
Costs associated with refinancing of debt											0
Other									77	60	(511)
Total other income (expenses)									179	163	(157)
Earnings before income taxes and equity in earnings of nonconsolidated subsidiaries									58,767	45,695	75,359
Income tax expense (benefit):
Current									20,270	23,261	25,277
Deferred income taxes									0	(6,224)	1,866
Total income tax expense (benefit)									20,270	17,037	27,143
Earnings before equity in earnings of nonconsolidated subsidiaries									38,497	28,658	48,216
Equity in earnings of nonconsolidated subsidiaries									66,128	(39,418)	19,509
Net earnings									104,625	(10,760)	67,725
Less: Earnings attributable to noncontrolling interests									0	0	0
Net earnings attributable to Valmont Industries, Inc.									104,625	(10,760)	67,725
Non- Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales									1,195,812	1,238,609	1,456,053
Cost of sales									932,609	987,729	1,124,813
Gross profit									263,203	250,880	331,240
Selling, general and administrative expenses									182,002	207,484	204,243
Impairment of goodwill and intangible assets										41,970
Operating income									81,201	1,426	126,997
Other income (expense):
Interest expense									(696)	(1,069)	(2,518)
Interest income									2,720	3,184	5,649
Costs associated with refinancing of debt											0
Other									16,697	4,951	(5,594)
Total other income (expenses)									18,721	7,066	(2,463)
Earnings before income taxes and equity in earnings of nonconsolidated subsidiaries									99,922	8,492	124,534
Income tax expense (benefit):
Current									21,262	18,446	33,898
Deferred income taxes									(29,901)	1,040	4,859
Total income tax expense (benefit)									(8,639)	19,486	38,757
Earnings before equity in earnings of nonconsolidated subsidiaries									108,561	(10,994)	85,777
Equity in earnings of nonconsolidated subsidiaries									0	(247)	63
Net earnings									108,561	(11,241)	85,840
Less: Earnings attributable to noncontrolling interests									(5,159)	(5,216)	(5,342)
Net earnings attributable to Valmont Industries, Inc.									$ 103,402	$ (16,457)	$ 80,498