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Property, Plant and Equipment (Detail Textuals) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Property, Plant and Equipment [Line Items]    
Depreciation expense $ 509,000us-gaap_Depreciation $ 498,000us-gaap_Depreciation
Depreciation and amortization expense 652,000us-gaap_DepreciationAndAmortization 640,000us-gaap_DepreciationAndAmortization
Consumer Products Group    
Property, Plant and Equipment [Line Items]    
Construction in progress 2,529,000us-gaap_ConstructionInProgressGross
/ us-gaap_StatementBusinessSegmentsAxis
= svt_ConsumerProductsGroupMember
477,000us-gaap_ConstructionInProgressGross
/ us-gaap_StatementBusinessSegmentsAxis
= svt_ConsumerProductsGroupMember
Advanced Technology Group    
Property, Plant and Equipment [Line Items]    
Construction in progress 288,000us-gaap_ConstructionInProgressGross
/ us-gaap_StatementBusinessSegmentsAxis
= svt_AdvancedTechnologyGroupMember
477,000us-gaap_ConstructionInProgressGross
/ us-gaap_StatementBusinessSegmentsAxis
= svt_AdvancedTechnologyGroupMember
Land and building | Elma    
Property, Plant and Equipment [Line Items]    
Nominal amount of capital lease 5,000,000us-gaap_CapitalLeasedAssetsGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_LandAndBuildingMember
/ us-gaap_StatementGeographicalAxis
= svt_ElmaMember
 
Buildings    
Property, Plant and Equipment [Line Items]    
Accumulated amortization 2,811,000us-gaap_CapitalLeasesLesseeBalanceSheetAssetsByMajorClassAccumulatedDeprecation
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_BuildingMember
2,682,000us-gaap_CapitalLeasesLesseeBalanceSheetAssetsByMajorClassAccumulatedDeprecation
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_BuildingMember
Amortization expense $ 130,000us-gaap_AmortizationOfLeasedAsset
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_BuildingMember
$ 130,000us-gaap_AmortizationOfLeasedAsset
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_BuildingMember