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STOCKHOLDERS' EQUITY (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Total stock-based compensation expense $ 21,416us-gaap_AllocatedShareBasedCompensationExpense $ 111,636us-gaap_AllocatedShareBasedCompensationExpense $ 228,485us-gaap_AllocatedShareBasedCompensationExpense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of options outstanding (in shares) 759,958us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 1,167,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 1,182,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Number of shares available for grant (in shares) 728,708us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant    
Stock-based compensation expense 21,416us-gaap_ShareBasedCompensation 111,636us-gaap_ShareBasedCompensation 228,485us-gaap_ShareBasedCompensation
Stock granted during period, value of stock options   165,000us-gaap_StockGrantedDuringPeriodValueSharebasedCompensation 109,000us-gaap_StockGrantedDuringPeriodValueSharebasedCompensation
Assumptions used to estimate the fair values of the stock options granted [Abstract]      
Risk-free interest rate (in hundredths) 1.66%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate 1.21%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate 0.69%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
Expected volatility (in hundredths) 32.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate 35.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate 54.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
Expected life (in years) 5 years 5 years 5 years
Dividend yield (in hundredths) 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
Weighted-average estimated fair value of options granted during the year 85,000bstc_WeightedAverageEstimatedFairValueOfOptionsGranted 79,000bstc_WeightedAverageEstimatedFairValueOfOptionsGranted 110,000bstc_WeightedAverageEstimatedFairValueOfOptionsGranted
Shares [Roll Forward]      
Outstanding, beginning of period (in shares) 1,167,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 1,182,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber  
Grants (in shares) 15,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 30,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 15,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Exercised (in shares) (407,042)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised (30,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised  
Forfeitures or expirations (in shares) (15,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod (15,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod  
Outstanding at end of year (in shares) 759,958us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 1,167,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 1,182,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Vested and expected to vest (in shares) 728,708us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber    
Exercisable (in shares) 728,708us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant    
Weighted Average Exercise Price [Roll Forward]      
Outstanding at beginning of year (in dollars per share) $ 9.03us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 8.90us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice  
Grants (in dollars per share) $ 26.48us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice $ 16.88us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice  
Exercised (in dollars per share) $ 5.27us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice $ 1.00us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice  
Forfeitures or expirations (in dollars per share) $ 26.48us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice $ 30.79us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice  
Outstanding at end of year (in dollars per share) $ 11.04us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 9.03us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 8.90us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Vested and expected to vest (in dollars per share) $ 10.43us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice    
Exercisable (in dollars per share) $ 10.43us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue    
Weighted Average Remaining Contractual Term [Roll Forward]      
Outstanding, beginning of period 3 years 1 month 13 days 3 years 7 months 24 days 4 years 5 months 26 days
Grants 10 years 10 years  
Exercised 0 years 0 years  
Forfeitures or expirations 0 years 0 years  
Outstanding at end of period 3 years 1 month 13 days 3 years 7 months 24 days 4 years 5 months 26 days
Vested and expected to vest 2 years 11 months 26 days    
Exercisable 2 years 11 months 26 days    
Aggregate Intrinsic Value [Roll Forward]      
Outstanding, beginning of period 15,420,965us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding 9,597,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding  
Grants $ 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGrantDateIntrinsicValue $ 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGrantDateIntrinsicValue  
Exercised 11,559,689us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue 602,100us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue  
Forfeitures and expirations $ 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageIntrinsicValue $ 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageIntrinsicValue  
Outstanding at end of period 23,483,235us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding 15,420,965us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding 9,597,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding
Vested and expected to vest 20,542,279us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue    
Exercisable 20,542,279us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue    
Stock options by exercise price [Abstract]      
Number of Shares Outstanding (in shares) 759,958us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions    
Weighted Average Life 3 years 1 month 13 days    
Weighted Average Exercise Price (in dollars per share) $ 11.04us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1    
Number of Shares Exercisable (in shares) 728,708us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions    
Weighted Average Option Price (in dollars per share) $ 10.43us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1    
Weighted Average Life 2 years 11 months 26 days    
Proceeds from stock option exercises 2,146,821us-gaap_ProceedsFromStockOptionsExercised 30,000us-gaap_ProceedsFromStockOptionsExercised 148,425us-gaap_ProceedsFromStockOptionsExercised
Closing price of Company stock (in dollars per share) $ 38.62us-gaap_SharePrice    
Unrecognized compensation cost 58,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions    
Weighted average period for recognition of unrecognized compensation cost (in years) 2 years 9 months    
0.83-1.00 [Member]      
Stock options by exercise price [Abstract]      
Range of Options Exercise Prices, lower limit (in dollars per share) $ 0.83us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeOneMember		    
Range of Options Exercise Prices, upper limit (in dollars per share) $ 1.00us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeOneMember		    
Number of Shares Outstanding (in shares) 247,500us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeOneMember		    
Weighted Average Life 1 year 4 months 17 days    
Weighted Average Exercise Price (in dollars per share) $ 0.91us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeOneMember		    
Number of Shares Exercisable (in shares) 247,500us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeOneMember		    
Weighted Average Option Price (in dollars per share) $ 0.91us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeOneMember		    
Weighted Average Life 1 year 4 months 17 days    
4.00-5.50 [Member]      
Stock options by exercise price [Abstract]      
Range of Options Exercise Prices, lower limit (in dollars per share) $ 4.00us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeTwoMember		    
Range of Options Exercise Prices, upper limit (in dollars per share) $ 5.50us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeTwoMember		    
Number of Shares Outstanding (in shares) 133,000us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeTwoMember		    
Weighted Average Life 2 years 6 months 4 days    
Weighted Average Exercise Price (in dollars per share) $ 4.78us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeTwoMember		    
Number of Shares Exercisable (in shares) 133,000us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeTwoMember		    
Weighted Average Option Price (in dollars per share) $ 4.78us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeTwoMember		    
Weighted Average Life 2 years 6 months 4 days    
13.24-15.85 [Member]      
Stock options by exercise price [Abstract]      
Range of Options Exercise Prices, lower limit (in dollars per share) $ 13.24us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeThreeMember		    
Range of Options Exercise Prices, upper limit (in dollars per share) $ 15.85us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeThreeMember		    
Number of Shares Outstanding (in shares) 121,958us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeThreeMember		    
Weighted Average Life 4 years 5 months 16 days    
Weighted Average Exercise Price (in dollars per share) $ 14.05us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeThreeMember		    
Number of Shares Exercisable (in shares) 121,958us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeThreeMember		    
Weighted Average Option Price (in dollars per share) $ 14.05us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeThreeMember		    
Weighted Average Life 4 years 5 months 16 days    
17.00-21.00 [Member]      
Stock options by exercise price [Abstract]      
Range of Options Exercise Prices, lower limit (in dollars per share) $ 17.00us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFourMember		    
Range of Options Exercise Prices, upper limit (in dollars per share) $ 21.00us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFourMember		    
Number of Shares Outstanding (in shares) 167,500us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFourMember		    
Weighted Average Life 4 years 3 months 18 days    
Weighted Average Exercise Price (in dollars per share) $ 19.50us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFourMember		    
Number of Shares Exercisable (in shares) 156,250us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFourMember		    
Weighted Average Option Price (in dollars per share) $ 19.61us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFourMember		    
Weighted Average Life 3 years 11 months 23 days    
26.43-29.21 [Member]      
Stock options by exercise price [Abstract]      
Range of Options Exercise Prices, lower limit (in dollars per share) $ 26.43us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFiveMember		    
Range of Options Exercise Prices, upper limit (in dollars per share) $ 29.21us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFiveMember		    
Number of Shares Outstanding (in shares) 90,000us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFiveMember		    
Weighted Average Life 4 years 10 months 2 days    
Weighted Average Exercise Price (in dollars per share) $ 28.28us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFiveMember		    
Number of Shares Exercisable (in shares) 70,000us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFiveMember		    
Weighted Average Option Price (in dollars per share) $ 28.02us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= bstc_ExercisePricesRangeFiveMember		    
Weighted Average Life 4 years 9 months 25 days    
2001 Stock Option Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares authorized for issuance (in shares) 2,050,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember		    
Exercise price per share of common stock (in hundredths) 100.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember		    
Number of installments for options vest and become exercisable 4bstc_NumberOfInstallmentsForOptionsVestAndBecomeExercisable
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember		    
Options expiry period (in years) 10 years    
Number of options outstanding (in shares) 759,958us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember		    
Number of shares available for grant (in shares) 239,098us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember		    
Shares [Roll Forward]      
Outstanding at end of year (in shares) 759,958us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember		    
Exercisable (in shares) 239,098us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember		    
2001 Stock Option Plan [Member] | Qualified Incentive Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Exercise price per share of common stock (in hundredths) 110.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
/ us-gaap_AwardTypeAxis
= bstc_QualifiedIncentiveStockOptionsMember
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember		    
Minimum ownership percentage for qualified incentive stock options (in hundredths) 10.00%bstc_MinimumOwnershipPercentageForQualifiedIncentiveStockOptions
/ us-gaap_AwardTypeAxis
= bstc_QualifiedIncentiveStockOptionsMember
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember		    
Options expiry period (in years) 5 years    
Board of Directors [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock granted during period, value of stock options 123,000us-gaap_StockGrantedDuringPeriodValueSharebasedCompensation
/ us-gaap_TitleOfIndividualAxis
= us-gaap_BoardOfDirectorsChairmanMember		    
Shares [Roll Forward]      
Grants (in shares) 15,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_TitleOfIndividualAxis
= us-gaap_BoardOfDirectorsChairmanMember		    
Non-Employee [Member] | 2001 Stock Option Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock-based compensation expense 0us-gaap_ShareBasedCompensation
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember
/ us-gaap_TitleOfIndividualAxis
= bstc_NonEmployeeConsultantsMember		 79,049us-gaap_ShareBasedCompensation
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember
/ us-gaap_TitleOfIndividualAxis
= bstc_NonEmployeeConsultantsMember		 109,479us-gaap_ShareBasedCompensation
/ us-gaap_PlanNameAxis
= bstc_TwoZeroZeroOneStockOptionPlanMember
/ us-gaap_TitleOfIndividualAxis
= bstc_NonEmployeeConsultantsMember
Research and Development [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Total stock-based compensation expense 0us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_ResearchAndDevelopmentExpenseMember		 92,249us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_ResearchAndDevelopmentExpenseMember		 171,217us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_ResearchAndDevelopmentExpenseMember
General and Administrative [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Total stock-based compensation expense $ 21,416us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_GeneralAndAdministrativeExpenseMember		 $ 19,387us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_GeneralAndAdministrativeExpenseMember		 $ 57,268us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_GeneralAndAdministrativeExpenseMember