GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 27, 2014	Sep. 27, 2014	Dec. 28, 2013
Current assets:
Cash and cash equivalents	$ 312,851	$ 371,579	$ 452,218	$ 613,706
Receivables, net	501,403	536,918
Inventories	368,290	359,522
Prepaid expenses	52,208	56,912
Refundable and deferred income taxes	44,736	68,010
Total current assets	1,279,488	1,392,941
Property, plant and equipment, at cost	1,083,211	1,139,569
Less accumulated depreciation and amortization	539,976	533,116
Net property, plant and equipment	543,235	606,453
Goodwill	362,683	385,111
Other intangible assets	175,157	202,004
Investment in subsidiaries and intercompany accounts	0	0
Other assets	129,138	143,159
Total assets	2,489,701	2,729,668
Current liabilities:
Current installments of long-term debt	1,099	1,181
Notes payable to banks	1,496	13,952
Accounts payable	186,581	196,565
Accrued employee compensation and benefits	70,249	87,950
Accrued expenses	104,779	88,480
Dividends payable	8,649	9,086
Total current liabilities	(372,853)	(397,214)
Deferred income taxes	66,200	71,797
Long-term debt, excluding current installments	764,823	766,654
Defined benefit pension liability	129,600	150,124
Deferred compensation	48,637	47,932
Other noncurrent liabilities	41,811	45,542
Shareholders’ equity:
Common stock of $1 par value	27,900	27,900
Additional paid-in capital	0	0
Retained earnings	1,767,621	1,718,662
Accumulated other comprehensive income (loss)	(223,007)	(134,433)
Treasury stock	(552,780)	(410,296)
Total Valmont Industries, Inc. shareholders’ equity	1,019,734	1,201,833
Noncontrolling interest in consolidated subsidiaries	46,043	48,572
Total shareholders’ equity	1,065,777	1,250,405	1,358,686	1,544,846
Total liabilities and shareholders’ equity	2,489,701	2,729,668
Parent
Current assets:
Cash and cash equivalents	21,227	69,869	153,921	215,576
Receivables, net	137,255	158,316
Inventories	144,751	127,859
Prepaid expenses	11,397	7,087
Refundable and deferred income taxes	30,001	53,307
Total current assets	344,631	416,438
Property, plant and equipment, at cost	544,933	556,658
Less accumulated depreciation and amortization	330,102	319,899
Net property, plant and equipment	214,831	236,759
Goodwill	20,108	20,108
Other intangible assets	252	292
Investment in subsidiaries and intercompany accounts	1,356,897	1,446,989
Other assets	47,404	46,587
Total assets	1,984,123	2,167,173
Current liabilities:
Current installments of long-term debt	215	213
Notes payable to banks	0	0
Accounts payable	64,931	59,893
Accrued employee compensation and benefits	30,576	48,169
Accrued expenses	44,031	32,616
Dividends payable	8,649	9,086
Total current liabilities	(148,402)	(149,977)
Deferred income taxes	8,220	5,584
Long-term debt, excluding current installments	759,033	759,895
Defined benefit pension liability	0	0
Deferred compensation	43,485	41,803
Other noncurrent liabilities	5,249	8,081
Shareholders’ equity:
Common stock of $1 par value	27,900	27,900
Additional paid-in capital	0	0
Retained earnings	1,767,621	1,718,662
Accumulated other comprehensive income (loss)	(223,007)	(134,433)
Treasury stock	(552,780)	(410,296)
Total Valmont Industries, Inc. shareholders’ equity	1,019,734	1,201,833
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	1,019,734	1,201,833
Total liabilities and shareholders’ equity	1,984,123	2,167,173
Guarantors
Current assets:
Cash and cash equivalents	1,641	2,157	1,659	29,797
Receivables, net	68,885	68,414
Inventories	46,820	54,914
Prepaid expenses	612	502
Refundable and deferred income taxes	6,262	6,194
Total current assets	124,220	132,181
Property, plant and equipment, at cost	127,761	124,182
Less accumulated depreciation and amortization	69,069	65,493
Net property, plant and equipment	58,692	58,689
Goodwill	107,542	107,542
Other intangible assets	40,031	43,644
Investment in subsidiaries and intercompany accounts	848,126	825,236
Other assets	16	0
Total assets	1,178,627	1,167,292
Current liabilities:
Current installments of long-term debt	0	0
Notes payable to banks	0	0
Accounts payable	14,213	15,151
Accrued employee compensation and benefits	5,151	5,385
Accrued expenses	6,145	6,052
Dividends payable	0	0
Total current liabilities	(25,509)	(26,588)
Deferred income taxes	27,994	28,988
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	457,950	457,950
Additional paid-in capital	159,414	150,286
Retained earnings	571,936	552,676
Accumulated other comprehensive income (loss)	(64,176)	(49,196)
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	1,125,124	1,111,716
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	1,125,124	1,111,716
Total liabilities and shareholders’ equity	1,178,627	1,167,292
Non- Guarantors
Current assets:
Cash and cash equivalents	289,983	299,553	296,638	368,333
Receivables, net	295,263	310,188
Inventories	179,894	177,512
Prepaid expenses	40,199	49,323
Refundable and deferred income taxes	8,473	8,509
Total current assets	813,812	845,085
Property, plant and equipment, at cost	410,517	458,729
Less accumulated depreciation and amortization	140,805	147,724
Net property, plant and equipment	269,712	311,005
Goodwill	235,033	257,461
Other intangible assets	134,874	158,068
Investment in subsidiaries and intercompany accounts	921,673	887,055
Other assets	81,718	96,572
Total assets	2,456,822	2,555,246
Current liabilities:
Current installments of long-term debt	884	968
Notes payable to banks	1,496	13,952
Accounts payable	107,437	121,521
Accrued employee compensation and benefits	34,522	34,396
Accrued expenses	54,603	49,812
Dividends payable	0	0
Total current liabilities	(198,942)	(220,649)
Deferred income taxes	29,986	37,225
Long-term debt, excluding current installments	5,790	6,759
Defined benefit pension liability	129,600	150,124
Deferred compensation	5,152	6,129
Other noncurrent liabilities	36,562	37,461
Shareholders’ equity:
Common stock of $1 par value	648,682	648,682
Additional paid-in capital	1,107,536	1,098,408
Retained earnings	416,341	397,302
Accumulated other comprehensive income (loss)	(167,812)	(96,065)
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	2,004,747	2,048,327
Noncontrolling interest in consolidated subsidiaries	46,043	48,572
Total shareholders’ equity	2,050,790	2,096,899
Total liabilities and shareholders’ equity	2,456,822	2,555,246
Eliminations
Current assets:
Cash and cash equivalents	0	0	$ 0	$ 0
Receivables, net	0	0
Inventories	(3,175)	(763)
Prepaid expenses	0	0
Refundable and deferred income taxes	0	0
Total current assets	(3,175)	(763)
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	(3,126,696)	(3,159,280)
Other assets	0	0
Total assets	(3,129,871)	(3,160,043)
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)	(1,106,632)
Additional paid-in capital	(1,266,950)	(1,248,694)
Retained earnings	(988,277)	(949,978)
Accumulated other comprehensive income (loss)	231,988	145,261
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	(3,129,871)	(3,160,043)
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	(3,129,871)	(3,160,043)
Total liabilities and shareholders’ equity	$ (3,129,871)	$ (3,160,043)