GUARANTOR/NON-GUARANTOR FINANCIAL INFORMATION - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Jul. 01, 2017	Dec. 31, 2016	Jun. 25, 2016	Dec. 26, 2015
Current assets:
Cash and cash equivalents	$ 448,222	$ 399,948	$ 344,346	$ 349,074
Receivables, net	496,962	439,342
Inventories	382,648	350,028
Prepaid expenses, restricted cash, and other assets	43,545	57,297
Refundable income taxes	4,830	6,601
Total current assets	1,376,207	1,253,216
Property, plant and equipment, at cost	1,148,482	1,105,736
Less accumulated depreciation and amortization	628,375	587,401
Net property, plant and equipment	520,107	518,335
Goodwill	329,708	321,110
Other intangible assets	141,557	144,378
Investment in subsidiaries and intercompany accounts	0	0
Other assets	155,583	154,692
Total assets	2,523,162	2,391,731
Current liabilities:
Current installments of long-term debt	921	851
Notes payable to banks	376	746
Accounts payable	193,087	177,488
Accrued employee compensation and benefits	68,944	72,404
Accrued expenses	102,247	89,914
Dividends payable	8,472	8,445
Total current liabilities	(374,047)	(349,848)
Deferred income taxes	32,642	35,803
Long-term debt, excluding current installments	754,436	754,795
Defined benefit pension liability	194,517	209,470
Deferred compensation	47,799	44,319
Other noncurrent liabilities	17,275	14,910
Shareholders’ equity:
Common stock of $1 par value	27,900	27,900
Additional paid-in capital	0	0
Retained earnings	1,945,874	1,874,722
Accumulated other comprehensive loss	(305,799)	(346,359)
Treasury stock	(603,726)	(612,781)
Total Valmont Industries, Inc. shareholders’ equity	1,064,249	943,482
Noncontrolling interest in consolidated subsidiaries	38,197	39,104
Total shareholders’ equity	1,102,446	982,586	994,171	965,211
Total liabilities and shareholders’ equity	2,523,162	2,391,731
Eliminations
Current assets:
Cash and cash equivalents	0	0	0	0
Receivables, net	0	0
Inventories	(4,222)	(4,154)
Prepaid expenses, restricted cash, and other assets	0	0
Refundable income taxes	0	0
Total current assets	(4,222)	(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	(3,544,140)	(3,270,540)
Other assets	0	0
Total assets	(3,548,362)	(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	(188,855)	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	(1,270,735)	(1,266,950)
Retained earnings	(1,286,973)	(1,250,087)
Accumulated other comprehensive loss	304,833	348,976
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	(3,359,507)	(3,274,694)
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	(3,359,507)	(3,274,694)
Total liabilities and shareholders’ equity	(3,548,362)	(3,274,694)
Parent
Current assets:
Cash and cash equivalents	94,099	67,225	62,149	62,281
Receivables, net	144,846	134,351
Inventories	137,534	126,669
Prepaid expenses, restricted cash, and other assets	6,141	13,271
Refundable income taxes	4,830	6,601
Total current assets	387,450	348,117
Property, plant and equipment, at cost	554,027	547,076
Less accumulated depreciation and amortization	364,591	352,960
Net property, plant and equipment	189,436	194,116
Goodwill	20,108	20,108
Other intangible assets	157	184
Investment in subsidiaries and intercompany accounts	1,367,336	1,279,413
Other assets	47,042	43,880
Total assets	2,011,529	1,885,818
Current liabilities:
Current installments of long-term debt	0	0
Notes payable to banks	0	0
Accounts payable	55,029	52,272
Accrued employee compensation and benefits	33,624	34,508
Accrued expenses	33,217	30,261
Dividends payable	8,472	8,445
Total current liabilities	(130,342)	(125,486)
Deferred income taxes	18,958	22,481
Long-term debt, excluding current installments	751,041	751,251
Defined benefit pension liability	0	0
Deferred compensation	42,492	39,476
Other noncurrent liabilities	4,447	3,642
Shareholders’ equity:
Common stock of $1 par value	27,900	27,900
Additional paid-in capital	0	0
Retained earnings	1,945,874	1,874,722
Accumulated other comprehensive loss	(305,799)	(346,359)
Treasury stock	(603,726)	(612,781)
Total Valmont Industries, Inc. shareholders’ equity	1,064,249	943,482
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	1,064,249	943,482
Total liabilities and shareholders’ equity	2,011,529	1,885,818
Guarantors
Current assets:
Cash and cash equivalents	4,422	6,071	4,022	4,008
Receivables, net	80,026	60,522
Inventories	43,536	45,457
Prepaid expenses, restricted cash, and other assets	814	880
Refundable income taxes	0	0
Total current assets	128,798	112,930
Property, plant and equipment, at cost	156,700	153,596
Less accumulated depreciation and amortization	81,154	76,776
Net property, plant and equipment	75,546	76,820
Goodwill	110,562	110,561
Other intangible assets	33,454	35,953
Investment in subsidiaries and intercompany accounts	1,155,599	901,758
Other assets	0	0
Total assets	1,503,959	1,238,022
Current liabilities:
Current installments of long-term debt	0	0
Notes payable to banks	0	0
Accounts payable	10,891	15,732
Accrued employee compensation and benefits	6,088	7,243
Accrued expenses	10,745	15,242
Dividends payable	0	0
Total current liabilities	(27,724)	(38,217)
Deferred income taxes	0	0
Long-term debt, excluding current installments	182,193	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	163,199	159,414
Retained earnings	669,177	646,749
Accumulated other comprehensive loss	3,711	(64,313)
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	1,294,037	1,199,800
Noncontrolling interest in consolidated subsidiaries	0	0
Total shareholders’ equity	1,294,037	1,199,800
Total liabilities and shareholders’ equity	1,503,959	1,238,022
Non- Guarantors
Current assets:
Cash and cash equivalents	349,701	326,652	$ 278,175	$ 282,785
Receivables, net	272,090	244,469
Inventories	205,800	182,056
Prepaid expenses, restricted cash, and other assets	36,590	43,146
Refundable income taxes	0	0
Total current assets	864,181	796,323
Property, plant and equipment, at cost	437,755	405,064
Less accumulated depreciation and amortization	182,630	157,665
Net property, plant and equipment	255,125	247,399
Goodwill	199,038	190,441
Other intangible assets	107,946	108,241
Investment in subsidiaries and intercompany accounts	1,021,205	1,089,369
Other assets	108,541	110,812
Total assets	2,556,036	2,542,585
Current liabilities:
Current installments of long-term debt	921	851
Notes payable to banks	376	746
Accounts payable	127,167	109,484
Accrued employee compensation and benefits	29,232	30,653
Accrued expenses	58,285	44,411
Dividends payable	0	0
Total current liabilities	(215,981)	(186,145)
Deferred income taxes	13,684	13,322
Long-term debt, excluding current installments	10,057	3,544
Defined benefit pension liability	194,517	209,470
Deferred compensation	5,307	4,843
Other noncurrent liabilities	12,823	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	617,796	603,338
Accumulated other comprehensive loss	(308,544)	(284,663)
Treasury stock	0	0
Total Valmont Industries, Inc. shareholders’ equity	2,065,470	2,074,894
Noncontrolling interest in consolidated subsidiaries	38,197	39,104
Total shareholders’ equity	2,103,667	2,113,998
Total liabilities and shareholders’ equity	$ 2,556,036	$ 2,542,585