Financing - Additional Information (Detail) (Oxford [Member], USD $)	9 Months Ended
	Sep. 30, 2014 Installment
Oxford [Member]
Debt Instrument [Line Items]
Borrowing capacity under the Loan & security agreement	$ 3,000,000
Basis spread on fixed interest rate set at time of advance	7.27%
Minimum interest rate	7.50%
Description of interest rate	Each equipment advance will include interest at a fixed interest rate equal to the greater of 7.5% per annum and 7.27% plus the three-month U.S. Libor Rate per annum
Debt instrument payment terms	The principal amount of each equipment advance will be repaid in 36 monthly installments commencing on the applicable amortization date, which is July 1, 2015 for any equipment advance made on or before June 30, 2015, and is the first monthly payment date for any equipment advance made on or after July 1, 2015. Monthly installments payable prior to July 1, 2015 will consist of accrued interest only and monthly installments payable on or after July 1, 2015 will consist of principal and accrued interest
Debt instrument number of installments that include principal payable	36
Final payment of additional interest as a percentage of aggregate amount advanced	5.70%
Weighted average annual effective interest rate	11.10%
Minimum prepayment fee interest rate percentage	1.00%
Maximum prepayment fee interest rate percentage	3.00%
Advance received under loan and security agreement	893,000
Amount available for borrowing under agreement	$ 2,107,000
Outstanding loan balance, default interest rate	5.00%