Quarterly report pursuant to Section 13 or 15(d)

Investments at Fair Value - Additional Information (Detail)

v2.4.0.8
Investments at Fair Value - Additional Information (Detail) (USD $)
 3 Months Ended 9 Months Ended 9 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Jun. 30, 2014
Dec. 31, 2013
Apr. 18, 2014
Stock Option [Member]
Sep. 30, 2014
Argus Neurooptics LLC [Member]
Mar. 17, 2014
Argus Neurooptics LLC [Member]
Sep. 30, 2014
Argus Neurooptics LLC [Member]
Class A Preferred Stock [Member]
Schedule of Equity Method Investments [Line Items]                    
Equity Method Investments                 $ 250,000  
Equity Method Investment Ownership Percentage         100.00%       35.00%  
Shares Received Under Purchase Agreement                   13,409,962
Percentage of Shares Received Under Purchase Agreement                   83.00%
Preferred Units, Issued                   16,091,954
Percentage of Revenue Share Amount               5.00%    
Short-term Investments 52,000   52,000     0 243,000      
Investment Options, Expiration Date Sep. 30, 2014   Sep. 30, 2014              
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases     50,000              
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) 293,000 0 293,000 0            
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net     $ 293,000