Quarterly report pursuant to Section 13 or 15(d)

Debt and Interest- Additional Information (Detail)

Debt and Interest- Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended
Mar. 29, 2019
Mar. 31, 2019
Debt [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage   2.50%
Debt Instrument, Description of Variable Rate Basis   9.0% plus one-month LIBOR Rate
Debt Instrument, Redemption, Description At its option, upon ten business days’ prior written notice to Horizon, Mustang may prepay all or any portion greater than or equal to $500,000 of each of the outstanding advances by paying the entire principal balance (or portion thereof) and all accrued and unpaid interest, subject to a prepayment charge of 4.0% of the then outstanding principal balance of each advance if such advance is prepaid on or before the Loan Amortization Date (as defined in the Loan Agreement), 3% if such advance is prepaid after the Loan Amortization Date applicable to such Loan, but on or prior to twelve months following the Loan Amortization Date, and 2% thereafter. In addition, a final payment equal to $0.3 million for each advance (i.e., $0.8 million in aggregate with respect to the initial $15.0 million) is due on the maturity date or other date of payment in full. Amounts outstanding during an event of default shall be payable on demand and shall accrue interest at an additional rate of 5.0% per annum of the past due amount outstanding.  
Debt Instrument, Debt Default, Description of Violation or Event of Default The events of default under the Loan Agreement include, among other things, without limitation, and subject to customary grace periods, (1) Mustang’s failure to make any payments of principal or interest under the Loan Agreement, promissory notes or other loan documents, (2) Mustang’s breach or default in the performance of any covenant under the Loan Agreement, (3) the occurrence of a material adverse change, (4) Mustang making a false or misleading representation or warranty in any material respect, (5) Mustang’s insolvency or bankruptcy, (6) certain attachments or judgments on the Mustang’s assets, (7) the occurrence of any material default under certain agreements or obligations of Mustang involving indebtedness in excess of $0.3 million or (8) failing to maintain minimum monthly cash balances which range from approximately $8.0 to $13.0 million over the term of the loan. If an event of default occurs, Horizon is entitled to take enforcement action, including acceleration of amounts due under the Loan Agreement.  
Percentage of Warrants Included in Debt 5.00%  
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right 288,184  
Class of Warrant or Right, Exercise Price of Warrants or Rights $ 3.47  
Warrants Not Settleable in Cash, Fair Value Disclosure $ 900,000  
Horizon Technology Finance Corporation [Member]    
Debt [Line Items]    
Legal Fees 1,200,000  
Line of Credit Facility, Commitment Fee Amount 200,000  
Reimbursement of Legal Fees 30,000  
Mustang Two Thousand Nineteen Venture Debt [Member]    
Debt [Line Items]    
Line of Credit Facility, Current Borrowing Capacity 20,000,000  
Line of Credit Facility, Maximum Borrowing Capacity 15,000,000  
Line of Credit Facility, Remaining Borrowing Capacity $ 5,000,000