Property and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, Plant, And Equipment, Gross	$ 187	$ 26,910
Less accumulated depreciation and amortization	(164)	(15,615)
Property and equipment, net	$ 23	11,295
Laboratory Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	5 years
Property, Plant, And Equipment, Gross		7,671
Computers Equipment And Software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	3 years
Property, Plant, And Equipment, Gross	$ 187	3,913
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful life	5 years
Property, Plant, And Equipment, Gross		893
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Leasehold improvements	Shorter of asset’s useful life or remaining term of lease
Property, Plant, And Equipment, Gross		$ 14,433