Summary of Significant Accounting Policies - Estimated Useful Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2013
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment useful life	5 years
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment useful life	3 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment useful life description	Shorter of asset's useful life or remaining term of lease
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment useful life	5 years
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment useful life	5 years