Molecular Templates, Inc. Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Segment	Dec. 31, 2011	Mar. 16, 2011	Oct. 05, 2009
Accounting Policies [Line Items]
Shares of common stock and warrants exercisable	56,431,207	49,128,475	340,472	248,690
Warrants issued			136,186	99,475
Reportable segment	1
Sutter Hill [Member]
Accounting Policies [Line Items]
Shares of common stock and warrants exercisable			952,380	1,570,980
Warrants issued			380,952	628,264
Three Arch Management III, L.L.C. [Member]
Accounting Policies [Line Items]
Shares of common stock and warrants exercisable				1,047,120
Warrants issued				418,847
Agreements with Merck KGaA [Member]
Accounting Policies [Line Items]
Collaboration agreement upfront payment	25
Milestone payments received	72.5
Potential milestone payments	12.5
Percentage of payment to be made by Merck for worldwide development expenses	70.00%
Agreements with Merck KGaA [Member] \| Subsequent event [Member]
Accounting Policies [Line Items]
Milestone payments received	42.5
Furniture and Equipment [Member]
Accounting Policies [Line Items]
Property and equipment, estimated useful lives	3 years
Leasehold improvements [Member] \| Minimum [Member]
Accounting Policies [Line Items]
Property and equipment, estimated useful lives	4 years
Leasehold improvements [Member] \| Maximum [Member]
Accounting Policies [Line Items]
Property and equipment, estimated useful lives	6 years