Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies - Additional Information (Detail)

v2.4.1.9
Commitments and Contingencies - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Other Commitments [Line Items]      
Rent expense $ 0.8us-gaap_OperatingLeasesRentExpenseNet $ 0.6us-gaap_OperatingLeasesRentExpenseNet $ 0.7us-gaap_OperatingLeasesRentExpenseNet
Purchase commitments 3.1us-gaap_LongTermPurchaseCommitmentAmount    
Non-cancelable Facility Sublease beginning October 1, 2011 [Member]      
Other Commitments [Line Items]      
Square feet of laboratory space and office space 28,650us-gaap_AreaOfRealEstateProperty
/ us-gaap_LeaseArrangementTypeAxis
= thld_NonCancelableFacilitySubleaseBeginningOctoberFirstTwoThousandElevenMember 		   
Lease agreement expiration date Apr. 30, 2017    
Aggregate rent over life of lease 3.4thld_AggregateRentForLease
/ us-gaap_LeaseArrangementTypeAxis
= thld_NonCancelableFacilitySubleaseBeginningOctoberFirstTwoThousandElevenMember 		   
Security deposit for lease 0.06us-gaap_SecurityDeposit
/ us-gaap_LeaseArrangementTypeAxis
= thld_NonCancelableFacilitySubleaseBeginningOctoberFirstTwoThousandElevenMember 		   
Non-cancelable Facility Sublease beginning December 1, 2013 [Member]      
Other Commitments [Line Items]      
Square feet of laboratory space and office space 7,934us-gaap_AreaOfRealEstateProperty
/ us-gaap_LeaseArrangementTypeAxis
= thld_NonCancelableFacilitySubleaseBeginningDecemberFirstTwoThousandThirteenMember 		   
Lease agreement expiration date Dec. 31, 2016    
Aggregate rent over life of lease $ 0.7thld_AggregateRentForLease
/ us-gaap_LeaseArrangementTypeAxis
= thld_NonCancelableFacilitySubleaseBeginningDecemberFirstTwoThousandThirteenMember