GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION - Condensed Consolidated Statements of Earnings (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 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	$ 632,575	$ 765,668	$ 1,985,096	$ 2,360,007
Cost of sales	475,824	566,168	1,493,343	1,733,048
Gross profit	156,751	199,500	491,753	626,959
Selling, general and administrative expenses	104,539	111,697	327,858	335,532
Impairment of goodwill and intangible assets	15,200	0	15,200	0
Operating income	37,012	87,803	148,695	291,427
Other income (expense):
Interest expense	(11,120)	(8,716)	(33,480)	(25,217)
Interest income	905	1,477	2,395	4,793
Costs associated with refinancing of debt	0	(38,705)	0	(38,705)
Other	(1,230)	(2,344)	(242)	(6,253)
Total other income (expenses)	(11,445)	(48,288)	(31,327)	(65,382)
Earnings before income taxes	25,567	39,515	117,368	226,045
Income tax expense (benefit):
Current	6,746	23,290	37,656	82,345
Deferred income taxes	5,272	(9,064)	5,217	(4,034)
Total income tax expense (benefit)	12,018	14,226	42,873	78,311
Earnings before equity in earnings of nonconsolidated subsidiaries	13,549	25,289	74,495	147,734
Equity in earnings of nonconsolidated subsidiaries	0	(4)	0	(34)
Net earnings	13,549	25,285	74,495	147,700
Less: Earnings attributable to noncontrolling interests	(1,483)	(1,726)	(3,817)	(4,185)
Net earnings attributable to Valmont Industries, Inc.	12,066	23,559	70,678	143,515
Parent
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales	249,121	313,775	889,408	1,069,059
Cost of sales	191,143	234,085	673,789	785,898
Gross profit	57,978	79,690	215,619	283,161
Selling, general and administrative expenses	44,432	48,560	143,387	146,514
Impairment of goodwill and intangible assets	0		0
Operating income	13,546	31,130	72,232	136,647
Other income (expense):
Interest expense	(10,822)	(8,061)	(32,548)	(23,427)
Interest income	(9)	2	4	28
Costs associated with refinancing of debt		(38,705)		(38,705)
Other	(2,123)	(196)	(3,020)	1,625
Total other income (expenses)	(12,954)	(46,960)	(35,564)	(60,479)
Earnings before income taxes	592	(15,830)	36,668	76,168
Income tax expense (benefit):
Current	(9,059)	9,296	(122)	38,489
Deferred income taxes	7,909	(12,430)	11,728	(6,601)
Total income tax expense (benefit)	(1,150)	(3,134)	11,606	31,888
Earnings before equity in earnings of nonconsolidated subsidiaries	1,742	(12,696)	25,062	44,280
Equity in earnings of nonconsolidated subsidiaries	10,324	36,255	45,616	99,235
Net earnings	12,066	23,559	70,678	143,515
Less: Earnings attributable to noncontrolling interests	0	0	0	0
Net earnings attributable to Valmont Industries, Inc.	12,066	23,559	70,678	143,515
Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales	114,766	120,016	312,804	380,327
Cost of sales	82,848	92,091	235,893	283,443
Gross profit	31,918	27,925	76,911	96,884
Selling, general and administrative expenses	11,154	12,145	33,542	37,806
Impairment of goodwill and intangible assets	0		0
Operating income	20,764	15,780	43,369	59,078
Other income (expense):
Interest expense	0	0	0	0
Interest income	2	60	6	356
Costs associated with refinancing of debt		0		0
Other	31	(149)	31	(501)
Total other income (expenses)	33	(89)	37	(145)
Earnings before income taxes	20,797	15,691	43,406	58,933
Income tax expense (benefit):
Current	8,423	6,206	18,273	19,718
Deferred income taxes	(478)	(342)	(1,062)	1,325
Total income tax expense (benefit)	7,945	5,864	17,211	21,043
Earnings before equity in earnings of nonconsolidated subsidiaries	12,852	9,827	26,195	37,890
Equity in earnings of nonconsolidated subsidiaries	1,254	8,446	6,435	17,469
Net earnings	14,106	18,273	32,630	55,359
Less: Earnings attributable to noncontrolling interests	0	0	0	0
Net earnings attributable to Valmont Industries, Inc.	14,106	18,273	32,630	55,359
Non- Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales	321,726	384,564	946,517	1,072,560
Cost of sales	255,424	292,722	747,075	826,120
Gross profit	66,302	91,842	199,442	246,440
Selling, general and administrative expenses	48,953	50,992	150,929	151,212
Impairment of goodwill and intangible assets	15,200		15,200
Operating income	2,149	40,850	33,313	95,228
Other income (expense):
Interest expense	(298)	(655)	(932)	(1,790)
Interest income	912	1,415	2,385	4,409
Costs associated with refinancing of debt		0		0
Other	862	(1,999)	2,747	(7,377)
Total other income (expenses)	1,476	(1,239)	4,200	(4,758)
Earnings before income taxes	3,625	39,611	37,513	90,470
Income tax expense (benefit):
Current	7,226	7,791	19,570	24,009
Deferred income taxes	(2,159)	3,708	(5,449)	1,242
Total income tax expense (benefit)	5,067	11,499	14,121	25,251
Earnings before equity in earnings of nonconsolidated subsidiaries	(1,442)	28,112	23,392	65,219
Equity in earnings of nonconsolidated subsidiaries	0	0	0	0
Net earnings	(1,442)	28,112	23,392	65,219
Less: Earnings attributable to noncontrolling interests	(1,483)	(1,726)	(3,817)	(4,185)
Net earnings attributable to Valmont Industries, Inc.	(2,925)	26,386	19,575	61,034
Eliminations
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales	(53,038)	(52,687)	(163,633)	(161,939)
Cost of sales	(53,591)	(52,730)	(163,414)	(162,413)
Gross profit	553	43	(219)	474
Selling, general and administrative expenses	0	0	0	0
Impairment of goodwill and intangible assets	0		0
Operating income	553	43	(219)	474
Other income (expense):
Interest expense	0	0	0	0
Interest income	0	0	0	0
Costs associated with refinancing of debt		0		0
Other	0	0	0	0
Total other income (expenses)	0	0	0	0
Earnings before income taxes	553	43	(219)	474
Income tax expense (benefit):
Current	156	(3)	(65)	129
Deferred income taxes	0	0	0	0
Total income tax expense (benefit)	156	(3)	(65)	129
Earnings before equity in earnings of nonconsolidated subsidiaries	397	46	(154)	345
Equity in earnings of nonconsolidated subsidiaries	(11,578)	(44,705)	(52,051)	(116,738)
Net earnings	(11,181)	(44,659)	(52,205)	(116,393)
Less: Earnings attributable to noncontrolling interests	0	0	0	0
Net earnings attributable to Valmont Industries, Inc.	$ (11,181)	$ (44,659)	$ (52,205)	$ (116,393)