Operating Matters and Liquidity - Additional Information (Detail) - USD ($)	1 Months Ended				12 Months Ended
	Aug. 31, 2016	Jul. 29, 2016	Dec. 23, 2014	May 17, 2013	Dec. 31, 2016	Dec. 31, 2015	Apr. 17, 2017	Mar. 31, 2017	Aug. 25, 2016	Aug. 09, 2013
Line of Credit Facility [Line Items]
Net Income Loss					$ (7,414,099)	$ (7,898,013)
Accumulated deficit					(136,402,424)	(128,988,325)
Cash					$ 2,657,214	$ 4,706,018
Subsequent Event [Member]
Line of Credit Facility [Line Items]
Class of Warrant or Right, Exercise Price of Warrants or Rights							$ 0.10438
Working Capital Deficit								$ 5,500,000
Cash								791,000
Accounts Payable and Accrued Liabilities								1,100,000
Subordinated Convertible Promissory Notes [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount							$ 1,000,000
Horizon Technology Finance Corporation [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount								$ 3,600,000
Lender Warrant 2016 [Member]
Line of Credit Facility [Line Items]
Class of Warrant or Right, Exercise Price of Warrants or Rights					$ 0.0994
Class of Warrant or Right, Number of Securities Called by Warrants or Rights					5,169,577
Class Of Warrant Or Rights Warrant Term					10 years
Venture Loan [Member]
Line of Credit Facility [Line Items]
Class of Warrant or Right, Exercise Price of Warrants or Rights			$ 0.1003
Class of Warrant or Right, Number of Securities Called by Warrants or Rights			2,492,523
Debt Instrument, Payment Terms			The loan was to be repaid in forty-five (45) monthly payments consisting of fifteen (15) monthly payments of only interest followed by thirty (30) equal monthly payments of principal and interest. In addition, at the end of the repayment term (or at early termination of the loan) a final payment equal to 4.5% of the loan would have been due and payable.
Proceeds from Issuance of Long-term Debt			$ 5,000,000
Warrants Expire Term			10 years
Debt Restructuring 2016 [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					11.27%	11.27%			11.00%
Debt Principal Amount Reduced Percentage					33.00%				33.00%	33.00%
Payments for Other Fees	$ 25,000
Legal Fees	$ 5,000
Debt Instrument, Increase (Decrease) for Period, Description	the final payment was increased from 4.5% of the loan, or $225,000, to 6.5% of the loan, or $325,000
December 2014 Private Placement [Member]
Line of Credit Facility [Line Items]
Sale of Stock, Consideration Received on Transaction			$ 5,025,000
2013 Warrants [Member]
Line of Credit Facility [Line Items]
Class of Warrant or Right, Exercise Price of Warrants or Rights				$ 0.1003
Class of Warrant or Right, Number of Securities Called by Warrants or Rights				50,099,700
Private Placement [Member]
Line of Credit Facility [Line Items]
Class of Warrant or Right, Exercise Price of Warrants or Rights					$ 0.1003
2014 warrants [Member]
Line of Credit Facility [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights			50,099,700
Warrants [Member]
Line of Credit Facility [Line Items]
Sale of Stock, Price Per Share		$ 0.0994
Sale of Stock, Consideration Received on Transaction		$ 56,262,571
Common Stock [Member]
Line of Credit Facility [Line Items]
Net Income Loss					$ 0
Common Stock [Member] | Private Placement [Member]
Line of Credit Facility [Line Items]
Sale of Stock, Consideration Received on Transaction		$ 5,600,000
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 0.0994
Class of Warrant or Right, Number of Securities Called by Warrants or Rights		56,262,571
Common Stock [Member] | May 2013 Private Placement [Member]
Line of Credit Facility [Line Items]
Sale of Stock, Price Per Share				$ 0.1003
Sale of Stock, Consideration Received on Transaction				$ 12,000,000