Annual report pursuant to Section 13 and 15(d)

Equity Incentive Plans and Stock Based Compensation - Additional Information (Detail)

v2.4.1.9
Equity Incentive Plans and Stock Based Compensation - Additional Information (Detail) (USD $)
 0 Months Ended 12 Months Ended 0 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
May 15, 2014
Dec. 31, 2011
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Additional shares authorized for issuance       7,250,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized 1,250,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized 1,250,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized    
Aggregate intrinsic value of options outstanding $ 5,400,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue     $ 5,400,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue        
Aggregate intrinsic value of options exercisable 5,100,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1     5,100,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1        
Options vested and expected to vest 8,100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber     8,100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber        
Aggregate intrinsic value of options vested and expected to vest 5,400,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue     5,400,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue        
Weighted average remaining contractual life of options vested and expected to vest       7 years 2 months 5 days        
Weighted average exercise price of options vested and expected to vest $ 3.68us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice     $ 3.68us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice        
Total intrinsic value of stock options exercised       200,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue 500,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue 1,700,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue    
Cash received from stock option exercises       100,000us-gaap_ProceedsFromStockOptionsExercised 100,000us-gaap_ProceedsFromStockOptionsExercised 600,000us-gaap_ProceedsFromStockOptionsExercised    
Tax benefit realized upon exercise of option       0us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions 0us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions 0us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions    
Offering period       24 months        
Purchase period       6 months        
Discount available to eligible employees related to employee stock purchase plan       85.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate        
Remaining shares available for issuance 4,423,493us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant 175,236us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant 498,411us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant 4,423,493us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant 175,236us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant 498,411us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant   1,077,784us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Stock-based compensation expense 5,400,000us-gaap_AllocatedShareBasedCompensationExpense 4,800,000us-gaap_AllocatedShareBasedCompensationExpense 2,800,000us-gaap_AllocatedShareBasedCompensationExpense 5,488,000us-gaap_AllocatedShareBasedCompensationExpense 4,922,000us-gaap_AllocatedShareBasedCompensationExpense 3,010,000us-gaap_AllocatedShareBasedCompensationExpense    
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans 10,100,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized     10,100,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized        
Unrecognized compensation cost related to unvested stock-based awards granted to employees under the stock option plans, period for recognition 2 years 4 months 21 days              
Non-employee stock-based compensation expense       $ 100,000us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims $ 100,000us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims $ 200,000us-gaap_IssuanceOfStockAndWarrantsForServicesOrClaims    
2004 Equity Incentive Plan                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Additional shares authorized for issuance       1,250,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEquityIncentivePlanMember 		       
Percentage of fair market value       100.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEquityIncentivePlanMember 		       
Terms of stock options granted       10 years        
Terms of stock options vested       4 years        
2014 Equity Incentive Plan                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Additional shares authorized for issuance             6,626,157us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= thld_TwoThousandAndFourteenEquityIncentivePlanMember 		 
Percentage of fair market value             100.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
/ us-gaap_PlanNameAxis
= thld_TwoThousandAndFourteenEquityIncentivePlanMember 		 
Terms of stock options granted       10 years        
Terms of stock options vested       4 years        
Shares authorized for issuance under the 2014 Equity Incentive Plan             6,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= thld_TwoThousandAndFourteenEquityIncentivePlanMember 		 
2004 Employee Stock Purchase Plan                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Additional shares authorized for issuance       100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEmployeeStockPurchasePlanMember 		100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEmployeeStockPurchasePlanMember 		     
Plan participants purchased shares       154,992us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEmployeeStockPurchasePlanMember 		167,245us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEmployeeStockPurchasePlanMember 		     
Average purchase price under 2004 Employee Stock Purchase Plan $ 3.74us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerShareWeightedAveragePriceOfSharesPurchased
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEmployeeStockPurchasePlanMember 		$ 1.69us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerShareWeightedAveragePriceOfSharesPurchased
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEmployeeStockPurchasePlanMember 		  $ 3.74us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerShareWeightedAveragePriceOfSharesPurchased
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEmployeeStockPurchasePlanMember 		$ 1.69us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerShareWeightedAveragePriceOfSharesPurchased
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEmployeeStockPurchasePlanMember 		     
Remaining shares available for issuance 180,904us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEmployeeStockPurchasePlanMember 		    180,904us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= thld_TwoThousandFourEmployeeStockPurchasePlanMember