GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION - Condensed Consolidated Statements of Earnings (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jun. 25, 2016	Jul. 01, 2017	Jun. 25, 2016
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	$ 712,737	$ 640,249	$ 1,350,210	$ 1,236,854
Cost of sales	529,457	465,132	1,002,325	900,768
Gross profit	183,280	175,117	347,885	336,086
Selling, general and administrative expenses	104,990	103,311	205,093	201,915
Operating income	78,290	71,806	142,792	134,171
Other income (expense):
Interest expense	(10,818)	(11,122)	(22,122)	(22,176)
Interest income	967	707	1,894	1,518
Other	(32)	1,252	1,167	(426)
Total other income (expenses)	(9,883)	(9,163)	(19,061)	(21,084)
Earnings before income taxes	68,407	62,643	123,731	113,087
Income tax expense:
Current	27,803	22,745	29,101	33,259
Deferred income taxes	(6,718)	(3,544)	7,347	2,215
Total income tax expense (benefit)	21,085	19,201	36,448	35,474
Earnings before equity in earnings of nonconsolidated subsidiaries	47,322	43,442	87,283	77,613
Equity in earnings of nonconsolidated subsidiaries	0	0	0	0
Net earnings	47,322	43,442	87,283	77,613
Less: Earnings attributable to noncontrolling interests	(1,658)	(1,416)	(2,640)	(2,618)
Net earnings attributable to Valmont Industries, Inc.	45,664	42,026	84,643	74,995
Eliminations
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales	(53,823)	(47,992)	(122,136)	(100,065)
Cost of sales	(54,610)	(47,025)	(122,207)	(98,505)
Gross profit	787	(967)	71	(1,560)
Selling, general and administrative expenses	0	0	0	0
Operating income	787	(967)	71	(1,560)
Other income (expense):
Interest expense	3,785	0	6,051	0
Interest income	(3,785)	0	(6,051)	0
Other	0	0	0	0
Total other income (expenses)	0	0	0	0
Earnings before income taxes	787	(967)	71	(1,560)
Income tax expense:
Current	233	(409)	(11)	(529)
Deferred income taxes	0	0	0	0
Total income tax expense (benefit)	233	(409)	(11)	(529)
Earnings before equity in earnings of nonconsolidated subsidiaries	554	(558)	82	(1,031)
Equity in earnings of nonconsolidated subsidiaries	(35,123)	(35,438)	(62,637)	(55,077)
Net earnings	(34,569)	(35,996)	(62,555)	(56,108)
Less: Earnings attributable to noncontrolling interests	0	0	0	0
Net earnings attributable to Valmont Industries, Inc.	(34,569)	(35,996)	(62,555)	(56,108)
Parent
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales	316,185	290,171	609,450	575,209
Cost of sales	233,535	211,675	450,021	419,536
Gross profit	82,650	78,496	159,429	155,673
Selling, general and administrative expenses	46,922	44,530	97,139	87,024
Operating income	35,728	33,966	62,290	68,649
Other income (expense):
Interest expense	(10,646)	(10,918)	(21,788)	(21,848)
Interest income	144	46	295	113
Other	1,167	699	2,521	324
Total other income (expenses)	(9,335)	(10,173)	(18,972)	(21,411)
Earnings before income taxes	26,393	23,793	43,318	47,238
Income tax expense:
Current	15,344	10,391	10,457	15,974
Deferred income taxes	(5,788)	1,068	5,539	3,487
Total income tax expense (benefit)	9,556	11,459	15,996	19,461
Earnings before equity in earnings of nonconsolidated subsidiaries	16,837	12,334	27,322	27,777
Equity in earnings of nonconsolidated subsidiaries	28,827	29,692	57,321	47,218
Net earnings	45,664	42,026	84,643	74,995
Less: Earnings attributable to noncontrolling interests	0	0	0	0
Net earnings attributable to Valmont Industries, Inc.	45,664	42,026	84,643	74,995
Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales	122,359	97,159	239,584	188,685
Cost of sales	91,374	71,234	182,863	139,096
Gross profit	30,985	25,925	56,721	49,589
Selling, general and administrative expenses	11,849	11,080	23,509	22,510
Operating income	19,136	14,845	33,212	27,079
Other income (expense):
Interest expense	(3,785)	(3)	(6,051)	(3)
Interest income	10	14	24	39
Other	15	15	31	27
Total other income (expenses)	(3,760)	26	(5,996)	63
Earnings before income taxes	15,376	14,871	27,216	27,142
Income tax expense:
Current	4,782	6,242	10,102	8,814
Deferred income taxes	0	(2,149)	0	0
Total income tax expense (benefit)	4,782	4,093	10,102	8,814
Earnings before equity in earnings of nonconsolidated subsidiaries	10,594	10,778	17,114	18,328
Equity in earnings of nonconsolidated subsidiaries	6,296	5,746	5,316	7,859
Net earnings	16,890	16,524	22,430	26,187
Less: Earnings attributable to noncontrolling interests	0	0	0	0
Net earnings attributable to Valmont Industries, Inc.	16,890	16,524	22,430	26,187
Non- Guarantors
Condensed consolidated financial information for the Company (Parent), the guarantor subsidiaries and the non-guarantor subsidiaries
Net sales	328,016	300,911	623,312	573,025
Cost of sales	259,158	229,248	491,648	440,641
Gross profit	68,858	71,663	131,664	132,384
Selling, general and administrative expenses	46,219	47,701	84,445	92,381
Operating income	22,639	23,962	47,219	40,003
Other income (expense):
Interest expense	(172)	(201)	(334)	(325)
Interest income	4,598	647	7,626	1,366
Other	(1,214)	538	(1,385)	(777)
Total other income (expenses)	3,212	984	5,907	264
Earnings before income taxes	25,851	24,946	53,126	40,267
Income tax expense:
Current	7,444	6,521	8,553	9,000
Deferred income taxes	(930)	(2,463)	1,808	(1,272)
Total income tax expense (benefit)	6,514	4,058	10,361	7,728
Earnings before equity in earnings of nonconsolidated subsidiaries	19,337	20,888	42,765	32,539
Equity in earnings of nonconsolidated subsidiaries	0	0	0	0
Net earnings	19,337	20,888	42,765	32,539
Less: Earnings attributable to noncontrolling interests	(1,658)	(1,416)	(2,640)	(2,618)
Net earnings attributable to Valmont Industries, Inc.	$ 17,679	$ 19,472	$ 40,125	$ 29,921