GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017
Current assets:
Cash and cash equivalents	$ 256,944		$ 313,210
Receivables, net	507,061		483,963
Inventories	406,546		383,566
Contract asset - costs and profits in excess of billings	123,926		112,525
Prepaid expenses and other assets	44,942		42,800
Refundable income taxes	8,579		4,576
Total current assets	1,347,998		1,340,640
Property, plant and equipment, at cost	1,225,838		1,160,865
Less accumulated depreciation and amortization	682,281		646,873
Net property, plant and equipment	543,557		513,992
Goodwill	424,188		385,207
Other intangible assets	189,014		175,956
Investment in subsidiaries and intercompany accounts	0		0
Other assets	206,982		114,479
Total assets	2,711,739		2,530,274
Current liabilities:
Current installments of long-term debt	774		779
Notes payable to banks	20,375		10,678
Accounts payable	228,137		218,115
Accrued employee compensation and benefits	65,723		79,291
Accrued expenses	174,163		91,942
Dividends payable	8,129		8,230
Total current liabilities	497,301		409,035
Deferred income taxes	43,774		43,489
Long-term debt, excluding current installments	765,558		741,822
Defined benefit pension liability	130,210		143,904
Deferred compensation	49,445		46,107
Other noncurrent liabilities	147,882		56,501
Shareholders’ equity:
Common stock of $1 par value	27,900		27,900
Additional paid-in capital	0		0
Retained earnings	2,085,594		2,027,596
Accumulated other comprehensive loss	(303,072)		(303,185)
Treasury stock	(728,680)		(692,549)
Total Valmont Industries, Inc. shareholders’ equity	1,081,742		1,059,762
Noncontrolling interest in consolidated subsidiaries	45,272		75,761
Total shareholders’ equity	1,127,014	$ 1,131,215	1,135,523	$ 1,149,824	$ 1,185,356	$ 1,151,795
Total liabilities and shareholders’ equity	2,711,739		2,530,274
Eliminations
Current assets:
Cash and cash equivalents	0		0
Receivables, net	0		0
Inventories	(2,576)		(2,402)
Contract asset - costs and profits in excess of billings	0		0
Prepaid expenses and other assets	0		0
Refundable income taxes	0		0
Total current assets	(2,576)		(2,402)
Property, plant and equipment, at cost	0		0
Less accumulated depreciation and amortization	0		0
Net property, plant and equipment	0		0
Goodwill	0		0
Other intangible assets	0		0
Investment in subsidiaries and intercompany accounts	(3,296,509)		(3,381,139)
Other assets	0		0
Total assets	(3,299,085)		(3,383,541)
Current liabilities:
Current installments of long-term debt	0		0
Notes payable to banks	0		0
Accounts payable	0		0
Accrued employee compensation and benefits	0		0
Accrued expenses	(909)		0
Dividends payable	0		0
Total current liabilities	(909)		0
Deferred income taxes	0		0
Long-term debt, excluding current installments	(124,233)		(166,729)
Defined benefit pension liability	0		0
Other noncurrent liabilities	0		0
Shareholders’ equity:
Common stock of $1 par value	(1,106,907)		(1,106,632)
Additional paid-in capital	(1,270,442)		(1,270,442)
Retained earnings	(1,096,017)		(1,092,093)
Accumulated other comprehensive loss	299,423		252,355
Treasury stock	0		0
Total Valmont Industries, Inc. shareholders’ equity	(3,173,943)		(3,216,812)
Noncontrolling interest in consolidated subsidiaries	0		0
Total shareholders’ equity	(3,173,943)		(3,216,812)
Total liabilities and shareholders’ equity	(3,299,085)		(3,383,541)
Parent
Current assets:
Cash and cash equivalents	87,608		104,256
Receivables, net	152,234		134,943
Inventories	141,709		138,158
Contract asset - costs and profits in excess of billings	61,754		50,271
Prepaid expenses and other assets	6,757		21,858
Refundable income taxes	8,579		4,576
Total current assets	458,641		454,062
Property, plant and equipment, at cost	601,146		579,046
Less accumulated depreciation and amortization	405,799		390,438
Net property, plant and equipment	195,347		188,608
Goodwill	20,108		20,108
Other intangible assets	49		76
Investment in subsidiaries and intercompany accounts	1,359,065		1,286,545
Other assets	94,400		47,674
Total assets	2,127,610		1,997,073
Current liabilities:
Current installments of long-term debt	0		0
Notes payable to banks	0		0
Accounts payable	67,877		68,304
Accrued employee compensation and benefits	32,552		41,418
Accrued expenses	101,998		25,936
Dividends payable	8,129		8,230
Total current liabilities	210,556		143,888
Deferred income taxes	14,402		14,376
Long-term debt, excluding current installments	734,265		733,964
Defined benefit pension liability	0		0
Other noncurrent liabilities	86,645		45,083
Shareholders’ equity:
Common stock of $1 par value	27,900		27,900
Additional paid-in capital	0		0
Retained earnings	2,085,594		2,027,596
Accumulated other comprehensive loss	(303,072)		(303,185)
Treasury stock	(728,680)		(692,549)
Total Valmont Industries, Inc. shareholders’ equity	1,081,742		1,059,762
Noncontrolling interest in consolidated subsidiaries	0		0
Total shareholders’ equity	1,081,742		1,059,762
Total liabilities and shareholders’ equity	2,127,610		1,997,073
Guarantors
Current assets:
Cash and cash equivalents	5,615		5,518
Receivables, net	88,774		75,204
Inventories	44,033		37,019
Contract asset - costs and profits in excess of billings	38,180		35,200
Prepaid expenses and other assets	8,736		746
Refundable income taxes	0		0
Total current assets	185,338		153,687
Property, plant and equipment, at cost	192,902		172,050
Less accumulated depreciation and amortization	98,864		93,374
Net property, plant and equipment	94,038		78,676
Goodwill	140,924		110,562
Other intangible assets	47,206		27,452
Investment in subsidiaries and intercompany accounts	1,097,380		1,161,612
Other assets	4,029		0
Total assets	1,568,915		1,531,989
Current liabilities:
Current installments of long-term debt	0		0
Notes payable to banks	0		0
Accounts payable	21,285		21,081
Accrued employee compensation and benefits	4,856		7,186
Accrued expenses	11,746		10,132
Dividends payable	0		0
Total current liabilities	37,887		38,399
Deferred income taxes	0		0
Long-term debt, excluding current installments	124,233		166,729
Defined benefit pension liability	0		0
Other noncurrent liabilities	3,214		620
Shareholders’ equity:
Common stock of $1 par value	457,950		457,950
Additional paid-in capital	162,906		162,906
Retained earnings	705,955		624,394
Accumulated other comprehensive loss	76,770		80,991
Treasury stock	0		0
Total Valmont Industries, Inc. shareholders’ equity	1,403,581		1,326,241
Noncontrolling interest in consolidated subsidiaries	0		0
Total shareholders’ equity	1,403,581		1,326,241
Total liabilities and shareholders’ equity	1,568,915		1,531,989
Non- Guarantors
Current assets:
Cash and cash equivalents	163,721		203,436
Receivables, net	266,053		273,816
Inventories	223,380		210,791
Contract asset - costs and profits in excess of billings	23,992		27,054
Prepaid expenses and other assets	29,449		20,196
Refundable income taxes	0		0
Total current assets	706,595		735,293
Property, plant and equipment, at cost	431,790		409,769
Less accumulated depreciation and amortization	177,618		163,061
Net property, plant and equipment	254,172		246,708
Goodwill	263,156		254,537
Other intangible assets	141,759		148,428
Investment in subsidiaries and intercompany accounts	840,064		932,982
Other assets	108,553		66,805
Total assets	2,314,299		2,384,753
Current liabilities:
Current installments of long-term debt	774		779
Notes payable to banks	20,375		10,678
Accounts payable	138,975		128,730
Accrued employee compensation and benefits	28,315		30,687
Accrued expenses	61,328		55,874
Dividends payable	0		0
Total current liabilities	249,767		226,748
Deferred income taxes	29,372		29,113
Long-term debt, excluding current installments	31,293		7,858
Defined benefit pension liability	130,210		143,904
Other noncurrent liabilities	58,023		10,798
Shareholders’ equity:
Common stock of $1 par value	648,957		648,682
Additional paid-in capital	1,107,536		1,107,536
Retained earnings	390,062		467,699
Accumulated other comprehensive loss	(376,193)		(333,346)
Treasury stock	0		0
Total Valmont Industries, Inc. shareholders’ equity	1,770,362		1,890,571
Noncontrolling interest in consolidated subsidiaries	45,272		75,761
Total shareholders’ equity	1,815,634		1,966,332
Total liabilities and shareholders’ equity	$ 2,314,299		$ 2,384,753