CONDENSED CONSOLIDATED STATEMENTS OF EARNINGS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Income Statement [Abstract]
Product sales	$ 2,447,219	$ 2,255,860	$ 2,338,132
Services sales	298,748	265,816	280,792
Net sales	2,745,967	2,521,676	2,618,924
Product cost of sales	1,860,087	1,682,355	1,804,055
Services cost of sales	204,112	183,078	193,836
Total cost of sales	2,064,199	1,865,433	1,997,891
Gross profit	681,768	656,243	621,033
Selling, general and administrative expenses	415,336	412,739	447,368
Impairment of goodwill and intangible assets	0	0	41,970
Operating income	266,432	243,504	131,695
Other income (expenses):
Interest expense	(44,645)	(44,409)	(44,621)
Interest income	4,737	3,105	3,296
Other	1,940	18,254	2,637
Total other income (expenses)	(37,968)	(23,050)	(38,688)
Earnings before income taxes and equity in earnings of nonconsolidated subsidiaries	228,464	220,454	93,007
Income tax expense (benefit):
Current	66,390	65,748	42,569
Deferred	39,755	(23,685)	4,858
Total income tax expense (benefit)	106,145	42,063	47,427
Comprehensive income (loss)	189,106	100,235	(91,836)
Earnings before equity in earnings of nonconsolidated subsidiaries	122,319	178,391	45,580
Equity in earnings of nonconsolidated subsidiaries	0	0	(247)
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	(12,568)	13,652	0
Net earnings	122,319	178,391	45,333
Less: Earnings attributable to noncontrolling interests	(6,079)	(5,159)	(5,216)
Net earnings attributable to Valmont Industries, Inc.	$ 116,240	$ 173,232	$ 40,117
Earnings per share:
Basic (in dollars per share)	$ 5.16	$ 7.68	$ 1.72
Diluted (in dollars per share)	5.11	7.63	1.71
Cash dividends declared per share (in dollars per share)	$ 1.500	$ 1.500	$ 1.500
Weighted average number of shares of common stock outstanding - Basic (in shares)	22,520	22,562	23,288
Weighted average number of shares of common stock outstanding - Diluted (in shares)	22,738	22,709	23,405