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Business Description and Summary of Significant Accounting Policies (Detail Textuals 1) (Sales Revenue, Advanced technology products, Customer Concentration Risk)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Concentration Risk [Line Items]    
Concentration risk, benchmark description
No other single customer of the ATG or CPG represented more than 10% of the consolidated revenues
  
Prime or subcontractors
    
Concentration Risk [Line Items]    
Concentration risk, percentage 15.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= svt_PrimeOrSubcontractorsMember
/ us-gaap_ProductOrServiceAxis
= svt_AdvancedTechnologyProductsMember		 17.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= svt_PrimeOrSubcontractorsMember
/ us-gaap_ProductOrServiceAxis
= svt_AdvancedTechnologyProductsMember
Customer One
    
Concentration Risk [Line Items]    
Concentration risk, percentage 31.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= svt_CustomerOneMember
/ us-gaap_ProductOrServiceAxis
= svt_AdvancedTechnologyProductsMember		 29.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= svt_CustomerOneMember
/ us-gaap_ProductOrServiceAxis
= svt_AdvancedTechnologyProductsMember
ATG customer
    
Concentration Risk [Line Items]    
Concentration risk, percentage 16.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= svt_AtgCustomerMember
/ us-gaap_ProductOrServiceAxis
= svt_AdvancedTechnologyProductsMember		 11.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= svt_AtgCustomerMember
/ us-gaap_ProductOrServiceAxis
= svt_AdvancedTechnologyProductsMember