Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended
	Aug. 31, 2011 sqft	Sep. 30, 2014
Redwood City, California [Member]
Operating Leased Assets [Line Items]
Operating facility lease area	5,740
Operating facility lease term		30 months
Operating facility lease term commencement date		2011-10
Menlo Park, California [Member]
Operating Leased Assets [Line Items]
Operating facility lease area		12,943
Operating facility lease term		39 months
Total obligation under lease		$ 1.6