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Long-Term Debt - Summary of long term debt (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Debt Instrument [Line Items]    
Long-term debt $ 4,461us-gaap_LongTermDebt $ 4,620us-gaap_LongTermDebt
Less current portion (548)us-gaap_LongTermDebtCurrent [1] (548)us-gaap_LongTermDebtCurrent
Long-term debt, Noncurrent 3,913us-gaap_LongTermDebtNoncurrent [1] 4,072us-gaap_LongTermDebtNoncurrent
Term loan payable to a financial institution    
Debt Instrument [Line Items]    
Long-term debt 2,533us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LoansPayableMember		 2,620us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LoansPayableMember
Term loan payable to a financial institution    
Debt Instrument [Line Items]    
Long-term debt $ 1,928us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= svt_TermLoanPayableTofinancialInstitutionMember		 $ 2,000us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= svt_TermLoanPayableTofinancialInstitutionMember
[1] Unaudited