Commitments and Contingencies - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Mar. 31, 2014 ft²	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Loss Contingencies [Line Items]
Rent expense		$ 763,000	$ 520,000	$ 241,000
Aggregate noncancellable purchase commitments		2,200,000
Other potential commitments		10,000,000
Pending or threatened legal proceedings		0
Maximum [Member]
Loss Contingencies [Line Items]
Commitment to make development and sales-related milestone payments		30,000,000
Menlo Park, California [Member]
Loss Contingencies [Line Items]
Operating facility lease area | ft²	12,900
Operating facility lease term	39 months
Total obligation under lease		$ 1,300,000
Menlo Park, California [Member] | Sublease Agreement [Member]
Loss Contingencies [Line Items]
Operating facility lease term		24 months
Total obligation under lease		$ 1,200,000
Lease commencement date		Jan. 01, 2016