CONDENSED CONSOLIDATED STATEMENTS OF EARNINGS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 24, 2016	Sep. 30, 2017	Sep. 24, 2016
Income Statement [Abstract]
Product sales	$ 602,080	$ 544,828	$ 1,807,539	$ 1,648,530
Services sales	78,699	65,419	223,450	198,571
Net sales	680,779	610,247	2,030,989	1,847,101
Product cost of sales	462,854	409,003	1,366,875	1,220,567
Services cost of sales	54,331	46,221	152,635	135,425
Total cost of sales	517,185	455,224	1,519,510	1,355,992
Gross profit	163,594	155,023	511,479	491,109
Selling, general and administrative expenses	103,671	101,783	308,764	303,698
Operating income	59,923	53,240	202,715	187,411
Other income (expenses):
Interest expense	(11,190)	(11,100)	(33,312)	(33,276)
Interest income	1,311	771	3,205	2,289
Other	517	878	1,684	452
Total other income (expenses)	(9,362)	(9,451)	(28,423)	(30,535)
Earnings before income taxes	50,561	43,789	174,292	156,876
Income tax expense:
Current	21,163	18,017	50,264	51,276
Deferred	(7,268)	(3,749)	79	(1,534)
Total income tax expense (benefit)	13,895	14,268	50,343	49,742
Earnings before equity in earnings of nonconsolidated subsidiaries	36,666	29,521	123,949	107,134
Equity in earnings of nonconsolidated subsidiaries	0	0	0	0
Net earnings	36,666	29,521	123,949	107,134
Less: Earnings attributable to noncontrolling interests	(1,458)	(1,348)	(4,098)	(3,966)
Net earnings attributable to Valmont Industries, Inc.	$ 35,208	$ 28,173	$ 119,851	$ 103,168
Earnings per share:
Basic (in dollars per share)	$ 1.56	$ 1.25	$ 5.33	$ 4.56
Diluted (in dollars per share)	1.55	1.24	5.28	4.54
Cash dividends declared per share (in dollars per share)	$ 0.375	$ 0.375	$ 1.125	$ 1.125
Weighted average number of shares of common stock outstanding - Basic (in shares)	22,527	22,505	22,505	22,602
Weighted average number of shares of common stock outstanding - Diluted (in shares)	22,751	22,659	22,717	22,741