GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 26, 2015	Sep. 26, 2015	Dec. 27, 2014
Current assets:
Cash and cash equivalents	$ 349,375	$ 349,074	$ 312,851	$ 371,579
Receivables, net	455,692	466,443
Inventories	379,625	340,672
Prepaid expenses, restricted cash, and other assets	69,231	46,137
Refundable income taxes	20,342	24,526
Total current assets	1,274,265	1,226,852
Property, plant and equipment, at cost	1,120,350	1,081,056
Less accumulated depreciation and amortization	594,710	548,567
Net property, plant and equipment	525,640	532,489
Goodwill	327,863	336,916
Other intangible assets	152,469	170,197
Investment in subsidiaries and intercompany accounts	0	0
Other assets	103,806	125,928
Total assets	2,384,043	2,392,382
Current liabilities:
Current installments of long-term debt	895	1,077
Notes payable to banks	853	976
Accounts payable	170,888	179,983
Accrued employee compensation and benefits	69,549	70,354
Accrued expenses	109,285	105,593
Dividends payable	8,455	8,571
Total current liabilities	(359,925)	(366,554)
Deferred income taxes	28,822	35,669
Long-term debt, excluding current installments	755,584	756,918
Defined benefit pension liability	156,524	179,323
Deferred compensation	47,783	48,417
Other noncurrent liabilities	33,104	40,290
Shareholders’ equity:
Common stock of $1 par value	27,900	27,900
Additional paid-in capital	0	0
Retained earnings	1,811,947	1,729,679
Accumulated other comprehensive loss	(265,969)	(267,218)
Treasury stock	(610,680)	(571,920)
Total Valmont Industries, Inc. shareholders’ equity	963,198	918,441
Noncontrolling interest in consolidated subsidiaries	39,103	46,770
Total shareholders’ equity	1,002,301	965,211	1,065,777	1,250,405
Total liabilities and shareholders’ equity	2,384,043	2,392,382
Parent
Current assets:
Cash and cash equivalents	47,301	62,281	21,227	69,869
Receivables, net	141,242	130,741
Inventories	144,070	132,222
Prepaid expenses, restricted cash, and other assets	14,426	9,900
Refundable income taxes	20,342	24,526
Total current assets	367,381	359,670
Property, plant and equipment, at cost	542,199	541,536
Less accumulated depreciation and amortization	349,386	334,471
Net property, plant and equipment	192,813	207,065
Goodwill	20,108	20,108
Other intangible assets	198	238
Investment in subsidiaries and intercompany accounts	1,280,566	1,239,228
Other assets	38,557	40,067
Total assets	1,899,623	1,866,376
Current liabilities:
Current installments of long-term debt	0	215
Notes payable to banks	0	0
Accounts payable	50,119	66,723
Accrued employee compensation and benefits	27,969	32,272
Accrued expenses	44,340	31,073
Dividends payable	8,455	8,571
Total current liabilities	(130,883)	(138,854)
Deferred income taxes	7,852	9,686
Long-term debt, excluding current installments	751,351	751,765
Defined benefit pension liability	0	0
Deferred compensation	42,564	43,485
Other noncurrent liabilities	3,775	4,145
Shareholders’ equity:
Common stock of $1 par value	27,900	27,900
Additional paid-in capital	0	0
Retained earnings	1,811,947	1,729,679
Accumulated other comprehensive loss	(265,969)	(267,218)
Treasury stock	(610,680)	(571,920)
Total Valmont Industries, Inc. shareholders’ equity	963,198	918,441
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	963,198	918,441
Total liabilities and shareholders’ equity	1,899,623	1,866,376
Guarantors
Current assets:
Cash and cash equivalents	5,818	4,008	1,641	2,157
Receivables, net	51,418	66,387
Inventories	43,403	38,379
Prepaid expenses, restricted cash, and other assets	690	766
Refundable income taxes	0	0
Total current assets	101,329	109,540
Property, plant and equipment, at cost	150,966	132,864
Less accumulated depreciation and amortization	76,463	69,956
Net property, plant and equipment	74,503	62,908
Goodwill	110,562	110,562
Other intangible assets	37,211	40,959
Investment in subsidiaries and intercompany accounts	858,852	813,779
Other assets	83	0
Total assets	1,182,540	1,137,748
Current liabilities:
Current installments of long-term debt	0	0
Notes payable to banks	0	0
Accounts payable	16,210	13,680
Accrued employee compensation and benefits	6,052	6,347
Accrued expenses	15,880	22,802
Dividends payable	0	0
Total current liabilities	(38,142)	(42,829)
Deferred income taxes	0	0
Long-term debt, excluding current installments	0	0
Defined benefit pension liability	0	0
Deferred compensation	0	0
Other noncurrent liabilities	5	0
Shareholders’ equity:
Common stock of $1 par value	457,950	457,950
Additional paid-in capital	159,414	159,414
Retained earnings	591,654	541,917
Accumulated other comprehensive loss	(64,625)	(64,362)
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	1,144,393	1,094,919
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	1,144,393	1,094,919
Total liabilities and shareholders’ equity	1,182,540	1,137,748
Non- Guarantors
Current assets:
Cash and cash equivalents	296,256	282,785	289,983	299,553
Receivables, net	263,032	269,315
Inventories	196,645	173,064
Prepaid expenses, restricted cash, and other assets	54,115	35,471
Refundable income taxes	0	0
Total current assets	810,048	760,635
Property, plant and equipment, at cost	427,185	406,656
Less accumulated depreciation and amortization	168,861	144,140
Net property, plant and equipment	258,324	262,516
Goodwill	197,193	206,246
Other intangible assets	115,060	129,000
Investment in subsidiaries and intercompany accounts	1,095,578	939,177
Other assets	65,166	85,861
Total assets	2,541,369	2,383,435
Current liabilities:
Current installments of long-term debt	895	862
Notes payable to banks	853	976
Accounts payable	104,559	99,580
Accrued employee compensation and benefits	35,528	31,735
Accrued expenses	49,065	51,718
Dividends payable	0	0
Total current liabilities	(190,900)	(184,871)
Deferred income taxes	20,970	25,983
Long-term debt, excluding current installments	4,233	5,153
Defined benefit pension liability	156,524	179,323
Deferred compensation	5,219	4,932
Other noncurrent liabilities	29,324	36,145
Shareholders’ equity:
Common stock of $1 par value	648,682	648,683
Additional paid-in capital	1,107,536	1,107,536
Retained earnings	546,184	354,727
Accumulated other comprehensive loss	(207,306)	(210,688)
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	2,095,096	1,900,258
Noncontrolling interest in consolidated subsidiaries	39,103	46,770
Total shareholders’ equity	2,134,199	1,947,028
Total liabilities and shareholders’ equity	2,541,369	2,383,435
Eliminations
Current assets:
Cash and cash equivalents	0	0	$ 0	$ 0
Receivables, net	0	0
Inventories	(4,493)	(2,993)
Prepaid expenses, restricted cash, and other assets	0	0
Refundable income taxes	0	0
Total current assets	(4,493)	(2,993)
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	(3,234,996)	(2,992,184)
Other assets	0	0
Total assets	(3,239,489)	(2,995,177)
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	0	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	(1,266,950)	(1,266,950)
Retained earnings	(1,137,838)	(896,644)
Accumulated other comprehensive loss	271,931	275,050
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	(3,239,489)	(2,995,177)
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	(3,239,489)	(2,995,177)
Total liabilities and shareholders’ equity	$ (3,239,489)	$ (2,995,177)