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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 27, 2014
item
Dec. 28, 2013
Fiscal year    
Length of fiscal year 364 days 364 days
Cash overdrafts    
Cash book overdrafts $ 18,038us-gaap_BankOverdrafts $ 21,713us-gaap_BankOverdrafts
Segments    
Number of Reportable Segments 4us-gaap_NumberOfReportableSegments  
Percentage of Sales to Total Consolidated Sales of Other Business Activities, Aggregated as Other, Maximum 10.00%vmi_PercentageOfSalesToTotalConsolidatedSalesOfOtherBusinessActivitiesAggregatedAsOtherMaximum  
Inventories    
Inventory valued at the lower of cost, determined on the last-in, first-out (LIFO) method, or market (as a percent) 44.00%us-gaap_PercentageOfLIFOInventory 43.00%us-gaap_PercentageOfLIFOInventory
Excess of replacement cost of inventories over the LIFO value $ 47,178us-gaap_ExcessOfReplacementOrCurrentCostsOverStatedLIFOValue $ 45,204us-gaap_ExcessOfReplacementOrCurrentCostsOverStatedLIFOValue
Minimum    
Principles of Consolidation    
Equity method investment in affiliates, ownership percentage 20.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
Fiscal year    
Length of fiscal year 364 days  
Maximum    
Principles of Consolidation    
Equity method investment in affiliates, ownership percentage 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Cost method investment in affiliates, ownership percentage 20.00%vmi_CostMethodInvestmentOwnershipPercentage
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Fiscal year    
Length of fiscal year 371 days