Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity (Deficit) - Outstanding Warrants Valuation Assumption (Detail)

v2.4.1.9
Stockholders' Equity (Deficit) - Outstanding Warrants Valuation Assumption (Detail) (USD $)
3 Months Ended 12 Months Ended 0 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Feb. 18, 2015
March 2011 Offering      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]      
Risk-free interest rate 0.26%us-gaap_FairValueAssumptionsRiskFreeInterestRate
/ us-gaap_CreationDateAxis
= thld_MarchTwoThousandElevenOfferingMember
0.67%us-gaap_FairValueAssumptionsRiskFreeInterestRate
/ us-gaap_CreationDateAxis
= thld_MarchTwoThousandElevenOfferingMember
 
Expected life (in years) 11 months 16 days 1 year 2 months 16 days  
Dividend yield 0.00%us-gaap_FairValueAssumptionsExpectedDividendRate
/ us-gaap_CreationDateAxis
= thld_MarchTwoThousandElevenOfferingMember
0.00%us-gaap_FairValueAssumptionsExpectedDividendRate
/ us-gaap_CreationDateAxis
= thld_MarchTwoThousandElevenOfferingMember
 
Volatility 52.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_CreationDateAxis
= thld_MarchTwoThousandElevenOfferingMember
49.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_CreationDateAxis
= thld_MarchTwoThousandElevenOfferingMember
 
Stock price $ 4.06us-gaap_SharePrice
/ us-gaap_CreationDateAxis
= thld_MarchTwoThousandElevenOfferingMember
$ 3.18us-gaap_SharePrice
/ us-gaap_CreationDateAxis
= thld_MarchTwoThousandElevenOfferingMember
 
February 2015 Offering      
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]      
Risk-free interest rate 1.34%us-gaap_FairValueAssumptionsRiskFreeInterestRate
/ us-gaap_ClassOfWarrantOrRightAxis
= thld_FebruaryTwoThousandFifteenOfferingMember
  1.52%us-gaap_FairValueAssumptionsRiskFreeInterestRate
/ us-gaap_ClassOfWarrantOrRightAxis
= thld_FebruaryTwoThousandFifteenOfferingMember
Expected life (in years) 4 years 10 months 21 days   5 years
Dividend yield 0.00%us-gaap_FairValueAssumptionsExpectedDividendRate
/ us-gaap_ClassOfWarrantOrRightAxis
= thld_FebruaryTwoThousandFifteenOfferingMember
   
Volatility 50.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_ClassOfWarrantOrRightAxis
= thld_FebruaryTwoThousandFifteenOfferingMember
  50.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_ClassOfWarrantOrRightAxis
= thld_FebruaryTwoThousandFifteenOfferingMember
Stock price $ 4.06us-gaap_SharePrice
/ us-gaap_ClassOfWarrantOrRightAxis
= thld_FebruaryTwoThousandFifteenOfferingMember
  $ 4.26us-gaap_SharePrice
/ us-gaap_ClassOfWarrantOrRightAxis
= thld_FebruaryTwoThousandFifteenOfferingMember