Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property Plant and Equipment Gross	$ 3,348	$ 7,635
Less accumulated depreciation and amortization	(3,339)	(7,551)
Property and equipment, net	9	84
Laboratory Equipment
Property, Plant and Equipment [Line Items]
Property Plant and Equipment Gross		3,778
Office and Computer Equipment
Property, Plant and Equipment [Line Items]
Property Plant and Equipment Gross	605	983
Purchased Software
Property, Plant and Equipment [Line Items]
Property Plant and Equipment Gross	166	166
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Property Plant and Equipment Gross	43	174
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property Plant and Equipment Gross	$ 2,534	$ 2,534