Loans Payable - Additional Information (Detail)						12 Months Ended
	Sep. 24, 2014 USD ($) $ / shares shares	May. 28, 2012 USD ($)	Mar. 31, 2012 USD ($)	Jun. 02, 2010 USD ($) $ / shares shares	May. 28, 2010 USD ($)	Dec. 31, 2015 USD ($) Installment	Dec. 31, 2014 USD ($)	Jun. 30, 2014 USD ($)	May. 31, 2012 USD ($)
Debt Instrument [Line Items]
Loan outstanding	$ 11,600,000					$ 10,000,000
Loan payable, end-of-term payment due						540,000
Deferred financing charge								$ 1,200,000	$ 1,300,000
Warrants issued to lenders as part of new loan agreement, shares of common stock to purchase | shares	608,696			156,641
Warrants issued to lenders as part of new loan agreement, exercise price | $ / shares	$ 1.15			$ 7.98
Warrants issued to lenders as part of new loan agreement, fair value	$ 400,000			$ 800,000			$ 413,000
Assumptions used in the Black-Scholes pricing model for warrant, volatility	71.81%
Assumptions used in the Black-Scholes pricing model for warrant, expected term	5 years
Assumptions used in the Black-Scholes pricing model for warrant, risk-free interest rate	1.82%
Maximum amount of debt conversion						$ 2,000,000
Amended Loan Agreement
Debt Instrument [Line Items]
Loan payable, effective interest rate	16.14%
Loans Payable | Security Agreement Hercules
Debt Instrument [Line Items]
Loan payable, aggregate principal amount			$ 26,500,000		$ 25,000,000
Loan payable, start date of first principal payment			Apr. 01, 2013
Loan payable, Commencement date					Jan. 01, 2012
Loan payable, number of installments of principal and interest | Installment						30
Loan payable, frequency of installments of principal and interest						30 equal monthly installments
Loan payable, due date						Jan. 01, 2016
Loan payable, description of interest rate terms						Per annum interest is payable on principal balance of both loans at the greater of 11.9% and an amount equal to 11.9% plus the prime rate of interest minus 4.75%, provided however, that the per annum interest shall not exceed 15.0%.
Loan payable, interest rate, base rate						11.90%
Loan payable, interest rate, additional rate deducted from base rate						4.75%
Loan payable, maximum per annum interest rate						15.00%
Loan issuance costs paid		$ 200,000
Debt instrument convertible beneficial conversion feature						$ 0
Loans Payable | Security Agreement Hercules | Minimum
Debt Instrument [Line Items]
Loan payable, interest rate						11.90%
Option to purchase equity, net cash proceeds of equity securities						$ 10,000,000
Loans Payable | Hercules Amended Loan Agreement
Debt Instrument [Line Items]
Loan payable, aggregate principal amount	$ 10,000,000					$ 10,000,000
Loan payable, Commencement date	Jan. 01, 2015
Loan payable, number of installments of principal and interest | Installment						12
Loan payable, frequency of installments of principal and interest						Monthly principal and interest payments
Loan payable, due date						Jan. 01, 2018
Loan payable, end-of-term payment due						$ 500,000
Liquidity ratio						125.00%
Option to purchase equity, description						the Company has agreed to maintain, with respect to the new loan of $10.0 million, a liquidity ratio equal to or greater than 1.25 to 1.00 of the then outstanding loan balance or the equivalent of $12.5 million in unrestricted and unencumbered cash and cash equivalents
Loans Payable | Hercules Amended Loan Agreement | Financial covenant
Debt Instrument [Line Items]
Unrestricted and unencumbered cash and cash equivalents						$ 12,500,000