GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016	Mar. 26, 2016	Dec. 26, 2015
Current assets:
Cash and cash equivalents	$ 425,216	$ 399,948	$ 387,714	$ 349,074
Receivables, net	455,044	439,342
Inventories	389,156	350,028
Prepaid expenses, restricted cash, and other assets	54,532	57,297
Refundable income taxes	7,325	6,601
Total current assets	1,331,273	1,253,216
Property, plant and equipment, at cost	1,129,787	1,105,736
Less accumulated depreciation and amortization	610,129	587,401
Net property, plant and equipment	519,658	518,335
Goodwill	324,061	321,110
Other intangible assets	142,000	144,378
Investment in subsidiaries and intercompany accounts	0	0
Other assets	149,896	154,692
Total assets	2,466,888	2,391,731
Current liabilities:
Current installments of long-term debt	860	851
Notes payable to banks	957	746
Accounts payable	194,525	177,488
Accrued employee compensation and benefits	65,663	72,404
Accrued expenses	112,231	89,914
Dividends payable	8,468	8,445
Total current liabilities	(382,704)	(349,848)
Deferred income taxes	39,030	35,803
Long-term debt, excluding current installments	754,523	754,795
Defined benefit pension liability	187,276	209,470
Deferred compensation	46,567	44,319
Other noncurrent liabilities	15,508	14,910
Shareholders’ equity:
Common stock of $1 par value	27,900	27,900
Additional paid-in capital	0	0
Retained earnings	1,906,161	1,874,722
Accumulated other comprehensive loss	(326,253)	(346,359)
Treasury stock	(604,969)	(612,781)
Total Valmont Industries, Inc. shareholders’ equity	1,002,839	943,482
Noncontrolling interest in consolidated subsidiaries	38,441	39,104
Total shareholders’ equity	1,041,280	982,586	980,151	965,211
Total liabilities and shareholders’ equity	2,466,888	2,391,731
Eliminations
Current assets:
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Inventories	(4,869)	(4,154)
Prepaid expenses, restricted cash, and other assets	0	0
Refundable income taxes	0	0
Total current assets	(4,869)	(4,154)
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	(3,790,478)	(3,270,540)
Other assets	0	0
Total assets	(3,795,347)	(3,274,694)
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	0	0
Dividends payable	0	0
Total current liabilities	0	0
Deferred income taxes	0	0
Long-term debt, excluding current installments	(187,827)	0
Defined benefit pension liability	0	0
Deferred compensation	0	0
Other noncurrent liabilities	0	0
Shareholders’ equity:
Common stock of $1 par value	(1,106,632)	(1,106,633)
Additional paid-in capital	(1,266,945)	(1,266,950)
Retained earnings	(1,563,522)	(1,250,087)
Accumulated other comprehensive loss	329,579	348,976
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	(3,607,520)	(3,274,694)
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	(3,607,520)	(3,274,694)
Total liabilities and shareholders’ equity	(3,795,347)	(3,274,694)
Parent
Current assets:
Cash and cash equivalents	93,149	67,225	76,634	62,281
Receivables, net	133,907	134,351
Inventories	143,773	126,669
Prepaid expenses, restricted cash, and other assets	8,913	13,271
Refundable income taxes	7,325	6,601
Total current assets	387,067	348,117
Property, plant and equipment, at cost	551,491	547,076
Less accumulated depreciation and amortization	359,317	352,960
Net property, plant and equipment	192,174	194,116
Goodwill	20,108	20,108
Other intangible assets	171	184
Investment in subsidiaries and intercompany accounts	1,319,342	1,279,413
Other assets	45,976	43,880
Total assets	1,964,838	1,885,818
Current liabilities:
Current installments of long-term debt	0	0
Notes payable to banks	0	0
Accounts payable	54,551	52,272
Accrued employee compensation and benefits	32,084	34,508
Accrued expenses	45,272	30,261
Dividends payable	8,468	8,445
Total current liabilities	(140,375)	(125,486)
Deferred income taxes	24,693	22,481
Long-term debt, excluding current installments	751,148	751,251
Defined benefit pension liability	0	0
Deferred compensation	41,327	39,476
Other noncurrent liabilities	4,456	3,642
Shareholders’ equity:
Common stock of $1 par value	27,900	27,900
Additional paid-in capital	0	0
Retained earnings	1,906,161	1,874,722
Accumulated other comprehensive loss	(326,253)	(346,359)
Treasury stock	(604,969)	(612,781)
Total Valmont Industries, Inc. shareholders’ equity	1,002,839	943,482
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	1,002,839	943,482
Total liabilities and shareholders’ equity	1,964,838	1,885,818
Guarantors
Current assets:
Cash and cash equivalents	5,479	6,071	4,566	4,008
Receivables, net	74,221	60,522
Inventories	49,322	45,457
Prepaid expenses, restricted cash, and other assets	852	880
Refundable income taxes	0	0
Total current assets	129,874	112,930
Property, plant and equipment, at cost	155,330	153,596
Less accumulated depreciation and amortization	79,023	76,776
Net property, plant and equipment	76,307	76,820
Goodwill	110,562	110,561
Other intangible assets	34,703	35,953
Investment in subsidiaries and intercompany accounts	1,171,413	901,758
Other assets	0	0
Total assets	1,522,859	1,238,022
Current liabilities:
Current installments of long-term debt	0	0
Notes payable to banks	0	0
Accounts payable	17,559	15,732
Accrued employee compensation and benefits	5,774	7,243
Accrued expenses	13,014	15,242
Dividends payable	0	0
Total current liabilities	(36,347)	(38,217)
Deferred income taxes	0	0
Long-term debt, excluding current installments	180,863	0
Defined benefit pension liability	0	0
Deferred compensation	0	0
Other noncurrent liabilities	5	5
Shareholders’ equity:
Common stock of $1 par value	457,950	457,950
Additional paid-in capital	159,414	159,414
Retained earnings	683,203	646,749
Accumulated other comprehensive loss	5,077	(64,313)
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	1,305,644	1,199,800
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	1,305,644	1,199,800
Total liabilities and shareholders’ equity	1,522,859	1,238,022
Non- Guarantors
Current assets:
Cash and cash equivalents	326,588	326,652	$ 306,514	$ 282,785
Receivables, net	246,916	244,469
Inventories	200,930	182,056
Prepaid expenses, restricted cash, and other assets	44,767	43,146
Refundable income taxes	0	0
Total current assets	819,201	796,323
Property, plant and equipment, at cost	422,966	405,064
Less accumulated depreciation and amortization	171,789	157,665
Net property, plant and equipment	251,177	247,399
Goodwill	193,391	190,441
Other intangible assets	107,126	108,241
Investment in subsidiaries and intercompany accounts	1,299,723	1,089,369
Other assets	103,920	110,812
Total assets	2,774,538	2,542,585
Current liabilities:
Current installments of long-term debt	860	851
Notes payable to banks	957	746
Accounts payable	122,415	109,484
Accrued employee compensation and benefits	27,805	30,653
Accrued expenses	53,945	44,411
Dividends payable	0	0
Total current liabilities	(205,982)	(186,145)
Deferred income taxes	14,337	13,322
Long-term debt, excluding current installments	10,339	3,544
Defined benefit pension liability	187,276	209,470
Deferred compensation	5,240	4,843
Other noncurrent liabilities	11,047	11,263
Shareholders’ equity:
Common stock of $1 par value	648,682	648,683
Additional paid-in capital	1,107,531	1,107,536
Retained earnings	880,319	603,338
Accumulated other comprehensive loss	(334,656)	(284,663)
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	2,301,876	2,074,894
Noncontrolling interest in consolidated subsidiaries	38,441	39,104
Total shareholders’ equity	2,340,317	2,113,998
Total liabilities and shareholders’ equity	$ 2,774,538	$ 2,542,585