Indebtedness - Additional Information (Detail) (USD $)	12 Months Ended		0 Months Ended			2 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 06, 2013	Feb. 01, 2013	Sep. 04, 2012	Jul. 31, 2010	Nov. 25, 2014	Dec. 02, 2014	Jun. 30, 2013	Nov. 30, 2014	Dec. 31, 2012	Sep. 30, 2012	May 31, 2010
Debt Instrument [Line Items]
Loss on establishment	$ (459,000)
Warrants issued								871,840
Warrants issued to purchase common shares, per share								$ 11.47
Interest expense recognized upon conversion		991,000
Bridge Financing
Debt Instrument [Line Items]
Warrants issued									275,589
Warrants issued to purchase common shares, per share	$ 0.06
Series B Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Issuance of series B convertible preferred stock upon the conversion of notes payable			2,060,986
Fair value of convertible note on the date of conversion			4,200,000
Convertible Notes [Member]
Debt Instrument [Line Items]
Convertible debt, conversion terms	Unless converted earlier, principal and accrued interest on the June 2013 Convertible Notes was due and payable (i) upon demand of investors holding June 2013 Convertible Notes having an aggregate principal amount outstanding equal to at least 70% of the aggregate principal amount of all of the June 2013 Convertible Notes then outstanding (the “Requisite Holders”) at any time on or after April 1, 2014, (ii) immediately upon default, including insolvency or bankruptcy, of the Company, or (iii) upon a Deemed Liquidation Event, as defined in the Company’s charter in effect at the time the June 2013 Convertible Notes were issued.
Difference between the proceeds and fair value of Convertible Notes	287,000
Convertible Notes [Member] | Bridge Financing
Debt Instrument [Line Items]
Debt instrument, amount financed									3,500,000
Silicon Valley Bank [Member]
Debt Instrument [Line Items]
Long-term debt, percentage bearing variable interest, percentage rate	5.00%
Term Loan [Member]
Debt Instrument [Line Items]
Line of credit facility, annual principal payment	24,000
Loss on establishment	500,000
Term Loan [Member] | Silicon Valley Bank [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity										15,000,000		5,000,000	1,500,000
Interest at a fixed per annum rate	7.00%	5.75%									5.75%		8.25%
Amount borrowed				3,000,000	2,000,000	1,500,000
Payment of original loan					500,000
Number of monthly payments	36 monthly payments
Principal amounts of final payments rate	6.00%
Outstanding principal balance	If the Company repays all or a portion of the loan prior to the applicable maturity date, it will pay SVB a prepayment penalty fee, based on a percentage of the then outstanding principal balance, equal to 3% if the prepayment occurs on or before 24 months after the funding date thereof, 1% if the prepayment occurs more than 24 months after, but on or before 36 months after, the funding date thereof, or 0% if the prepayment occurs more than 36 months after the funding date thereof.
Outstanding loan	10,000,000	4,600,000
Term Loan [Member] | Silicon Valley Bank [Member] | Prime Lending Rate [Member]
Debt Instrument [Line Items]
Interest rate for tranche	3.75%
Term Loan [Member] | Silicon Valley Bank [Member] | First Tranche [Member]
Debt Instrument [Line Items]
Amount borrowed							10,000,000
Payment of original loan							3,200,000
Term Loan [Member] | Silicon Valley Bank [Member] | Second Tranche [Member]
Debt Instrument [Line Items]
Amount borrowed	$ 5,000,000