Debt - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended	1 Months Ended
	Dec. 31, 2014		Dec. 31, 2013	May 23, 2014	Jun. 30, 2012	Jan. 31, 2013	May 28, 2014
Debt Instrument [Line Items]
Repayment of principal and accrued interest	$ 3,000,000
Debt Instrument, Unamortized Discount	108,122	[1]
Warrant exercise price per share	$ 16.73		$ 18.20
Warrant value recorded in equity	108,122
Loan and security agreement [Member]
Debt Instrument [Line Items]
Loan and security agreement, interest incurred	47,165		136,625
Silicon Valley Bank [Member] | Loan and security agreement [Member]
Debt Instrument [Line Items]
Loan and security agreement, maximum credit					3,000,000
Loan and security agreement, amount drawn						3,000,000
Loan and security agreement, interest rate					4.50%
Loan and security agreement, payback period					24 months
Repayment of principal and accrued interest				2,400,000
Debt Instrument, Unamortized Discount				38,000
Square 1 Bank [Member] | Maximum [Member]
Debt Instrument [Line Items]
Cash burn under credit facility	3.00
Square 1 Bank [Member] | Minimum [Member]
Debt Instrument [Line Items]
Cash burn under credit facility	1.00
Square 1 Bank [Member] | Loan and security agreement [Member]
Debt Instrument [Line Items]
Loan and security agreement, amount drawn	4,500,000
Loan and security agreement, available credit							4,500,000
Fixed interest rate	5.50%
Loan and security agreement, amount of other indebtedness	400,000
Warrants exercisable, stock issued	22,881
Warrant exercise price per share	$ 5.90
Warrant expiration period	10 years
Line of credit facility, loan origination cost	$ 83,000
Loan and security agreement, Amortization period	42 months

[1] Represents the initial fair value of the detachable warrants to purchase common stock issued in connection with the term debt, net of amortization.