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Note 4 - Cash and Cash Equivalents and Short-term Investments (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2014
Note 4 - Cash and Cash Equivalents and Short-term Investments (Details) [Line Items]      
Short-term Investments $ 0us-gaap_ShortTermInvestments   $ 0us-gaap_ShortTermInvestments
Proceeds from Sale of Available-for-sale Securities 49,874,000us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities 26,661,000us-gaap_ProceedsFromSaleOfAvailableForSaleSecurities  
Available-for-sale Securities, Gross Realized Gains 700,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGains 800,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGains  
Available-for-sale Securities, Gross Realized Losses 600,000us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses 0us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses  
Available-for-sale Securities, Gross Unrealized Gain (Loss) 0us-gaap_AvailableforsaleSecuritiesGrossUnrealizedGainLoss1 1,100,000us-gaap_AvailableforsaleSecuritiesGrossUnrealizedGainLoss1  
Investment Income, Interest 600,000us-gaap_InvestmentIncomeInterest 1,500,000us-gaap_InvestmentIncomeInterest  
Majority Owned Joint Ventures [Member]      
Note 4 - Cash and Cash Equivalents and Short-term Investments (Details) [Line Items]      
Restricted Cash and Cash Equivalents $ 400,000us-gaap_RestrictedCashAndCashEquivalents
/ us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis
= strl_MajorityOwnedJointVenturesMember
  $ 0us-gaap_RestrictedCashAndCashEquivalents
/ us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis
= strl_MajorityOwnedJointVenturesMember