GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION (Details 3) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015	Sep. 26, 2015	Dec. 27, 2014
Current assets:
Cash and cash equivalents	$ 492,805	$ 399,948	$ 349,074	$ 399,948	$ 371,579
Receivables, less allowance of $9,396 in 2017 and $10,250 in 2016	503,677	439,342
Inventories	420,948	350,028
Prepaid expenses, restricted cash, and other assets	43,643	57,297
Refundable income taxes	11,492	6,601
Total current assets	1,472,565	1,253,216
Property, plant and equipment, at cost	1,165,687	1,105,736
Less accumulated depreciation and amortization	646,759	587,401
Net property, plant and equipment	518,928	518,335
Goodwill	337,720	321,110	371,808
Other intangible assets	138,599	144,378
Investment in subsidiaries and intercompany accounts	0	0
Other assets, less allowance for doubtful receivables of $417 in 2017 and $8,741 in 2016	134,438	154,692
Total assets	2,602,250	2,391,731	2,392,382
Current liabilities:
Current installments of long-term debt	966	851
Notes payable to banks	161	746
Accounts payable	227,906	177,488
Accrued employee compensation and benefits	84,426	72,404
Accrued expenses	81,029	89,914
Dividends payable	8,510	8,445
Total current liabilities	(402,998)	(349,848)
Deferred income taxes	34,906	35,803
Long-term debt, excluding current installments	753,888	754,795
Defined benefit pension liability	189,552	209,470
Deferred compensation	48,526	44,319
Other noncurrent liabilities	20,585	14,910
Shareholders’ equity:
Common stock of $1 par value	27,900	27,900
Additional paid-in capital	0	0
Retained earnings	1,954,344	1,874,722
Accumulated other comprehensive income (loss)	(279,022)	(346,359)
Cost of treasury stock, common shares of 5,206,474 in 2017 and 5,379,106 in 2016	(590,386)	(612,781)
Total Valmont Industries, Inc. shareholders’ equity	1,112,836	943,482
Noncontrolling interest in consolidated subsidiaries	38,959	39,104
Total shareholders’ equity	1,151,795	982,586	965,211		1,250,405
Total liabilities and shareholders’ equity	2,602,250	2,391,731
Eliminations
Current assets:
Cash and cash equivalents	0	0	0		0
Receivables, less allowance of $9,396 in 2017 and $10,250 in 2016	0	0
Inventories	(3,848)	(4,154)
Prepaid expenses, restricted cash, and other assets	0	0
Refundable income taxes	0	0
Total current assets	(3,848)	(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	(3,525,162)	(3,270,540)
Other assets, less allowance for doubtful receivables of $417 in 2017 and $8,741 in 2016	0	0
Total assets	(3,529,010)	(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	(191,847)	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	(1,241,666)	(1,250,087)
Accumulated other comprehensive income (loss)	278,085	348,976
Cost of treasury stock, common shares of 5,206,474 in 2017 and 5,379,106 in 2016	0	0
Total Valmont Industries, Inc. shareholders’ equity	(3,337,163)	(3,274,694)
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	(3,337,163)	(3,274,694)
Total liabilities and shareholders’ equity	(3,529,010)	(3,274,694)
Parent
Current assets:
Cash and cash equivalents	83,329	67,225	62,281		69,869
Receivables, less allowance of $9,396 in 2017 and $10,250 in 2016	149,221	134,351
Inventories	160,444	126,669
Prepaid expenses, restricted cash, and other assets	8,607	13,271
Refundable income taxes	11,492	6,601
Total current assets	413,093	348,117
Property, plant and equipment, at cost	557,371	547,076
Less accumulated depreciation and amortization	368,668	352,960
Net property, plant and equipment	188,703	194,116
Goodwill	20,108	20,108
Other intangible assets	130	184
Investment in subsidiaries and intercompany accounts	1,416,446	1,279,413
Other assets, less allowance for doubtful receivables of $417 in 2017 and $8,741 in 2016	50,773	43,880
Total assets	2,089,253	1,885,818
Current liabilities:
Current installments of long-term debt	0	0
Notes payable to banks	0	0
Accounts payable	69,915	52,272
Accrued employee compensation and benefits	44,086	34,508
Accrued expenses	28,198	30,261
Dividends payable	8,510	8,445
Total current liabilities	(150,709)	(125,486)
Deferred income taxes	20,885	22,481
Long-term debt, excluding current installments	750,821	751,251
Defined benefit pension liability	0	0
Deferred compensation	42,928	39,476
Other noncurrent liabilities	11,074	3,642
Shareholders’ equity:
Common stock of $1 par value	27,900	27,900
Additional paid-in capital	0	0
Retained earnings	1,954,344	1,874,722
Accumulated other comprehensive income (loss)	(279,022)	(346,359)
Cost of treasury stock, common shares of 5,206,474 in 2017 and 5,379,106 in 2016	(590,386)	(612,781)
Total Valmont Industries, Inc. shareholders’ equity	1,112,836	943,482
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	1,112,836	943,482
Total liabilities and shareholders’ equity	2,089,253	1,885,818
Guarantors
Current assets:
Cash and cash equivalents	5,304	6,071	4,008		2,157
Receivables, less allowance of $9,396 in 2017 and $10,250 in 2016	82,995	60,522
Inventories	46,801	45,457
Prepaid expenses, restricted cash, and other assets	970	880
Refundable income taxes	0	0
Total current assets	136,070	112,930
Property, plant and equipment, at cost	160,767	153,596
Less accumulated depreciation and amortization	84,508	76,776
Net property, plant and equipment	76,259	76,820
Goodwill	110,562	110,561
Other intangible assets	30,955	35,953
Investment in subsidiaries and intercompany accounts	1,181,537	901,758
Other assets, less allowance for doubtful receivables of $417 in 2017 and $8,741 in 2016	0	0
Total assets	1,535,383	1,238,022
Current liabilities:
Current installments of long-term debt	0	0
Notes payable to banks	0	0
Accounts payable	18,039	15,732
Accrued employee compensation and benefits	8,749	7,243
Accrued expenses	9,621	15,242
Dividends payable	0	0
Total current liabilities	(36,409)	(38,217)
Deferred income taxes	0	0
Long-term debt, excluding current installments	185,078	0
Defined benefit pension liability	0	0
Deferred compensation	0	0
Other noncurrent liabilities	6	5
Shareholders’ equity:
Common stock of $1 par value	457,950	457,950
Additional paid-in capital	159,414	159,414
Retained earnings	622,044	646,749
Accumulated other comprehensive income (loss)	74,482	(64,313)
Cost of treasury stock, common shares of 5,206,474 in 2017 and 5,379,106 in 2016	0	0
Total Valmont Industries, Inc. shareholders’ equity	1,313,890	1,199,800
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	1,313,890	1,199,800
Total liabilities and shareholders’ equity	1,535,383	1,238,022
Non- Guarantors
Current assets:
Cash and cash equivalents	404,172	326,652	$ 282,785		$ 299,553
Receivables, less allowance of $9,396 in 2017 and $10,250 in 2016	271,461	244,469
Inventories	217,551	182,056
Prepaid expenses, restricted cash, and other assets	34,066	43,146
Refundable income taxes	0	0
Total current assets	927,250	796,323
Property, plant and equipment, at cost	447,549	405,064
Less accumulated depreciation and amortization	193,583	157,665
Net property, plant and equipment	253,966	247,399
Goodwill	207,050	190,441
Other intangible assets	107,514	108,241
Investment in subsidiaries and intercompany accounts	927,179	1,089,369
Other assets, less allowance for doubtful receivables of $417 in 2017 and $8,741 in 2016	83,665	110,812
Total assets	2,506,624	2,542,585
Current liabilities:
Current installments of long-term debt	966	851
Notes payable to banks	161	746
Accounts payable	139,952	109,484
Accrued employee compensation and benefits	31,591	30,653
Accrued expenses	43,210	44,411
Dividends payable	0	0
Total current liabilities	(215,880)	(186,145)
Deferred income taxes	14,021	13,322
Long-term debt, excluding current installments	9,836	3,544
Defined benefit pension liability	189,552	209,470
Deferred compensation	5,598	4,843
Other noncurrent liabilities	9,505	11,263
Shareholders’ equity:
Common stock of $1 par value	648,682	648,683
Additional paid-in capital	1,107,536	1,107,536
Retained earnings	619,622	603,338
Accumulated other comprehensive income (loss)	(352,567)	(284,663)
Cost of treasury stock, common shares of 5,206,474 in 2017 and 5,379,106 in 2016	0	0
Total Valmont Industries, Inc. shareholders’ equity	2,023,273	2,074,894
Noncontrolling interest in consolidated subsidiaries	38,959	39,104
Total shareholders’ equity	2,062,232	2,113,998
Total liabilities and shareholders’ equity	$ 2,506,624	$ 2,542,585