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Income Taxes - Additional Information (Detail) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2016
Sep. 30, 2015
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Jan. 31, 2017
Mar. 30, 2016
Dec. 28, 2015
Dec. 31, 2014
Income Tax Disclosure [Line Items]                    
Effective income tax rate       34.00% 34.00% 34.00%        
Tax benefit recognized       $ 0 $ 0 $ 0        
AMT credit carryforwards       736,000            
Unremitted earnings reversed           274,000        
Recognized tax benefit, voluntary disclosure agreements with several states           555,000        
Gain from equity method investment           5,000,000        
Provisional tax benefit due to new Tax Act       122,000            
Untaxed accumulated unremitted foreign earnings       813,000            
Valuation allowance, deferred tax assets       33,024,000 29,274,000          
Increases in equity of realization of deferred tax assets valuation allowance             $ 3,485,000      
Research and development tax credit carryforwards       20,019,000 13,967,000          
Accrued interest       1,104,000 946,000 830,000       $ 1,254,000
Net interest expense       6,000 6,000 $ 21,000        
Potential payment of interest       29,000 $ 25,000          
Scenario, Plan [Member]                    
Income Tax Disclosure [Line Items]                    
Effective income tax rate     21.00%              
Great Wall Semiconductor Corporation (GWS) [Member]                    
Income Tax Disclosure [Line Items]                    
Gain from equity method investment   $ 4,999,719   $ 4,999,719            
Gain from equity method investment for income tax purpose   4,999,719                
Gain (loss) on transaction for income tax purpose   $ 0                
Aegis Power Systems Inc [Member]                    
Income Tax Disclosure [Line Items]                    
Sale of ownership interest           49.00%     49.00%  
Converpower Corporation [Member]                    
Income Tax Disclosure [Line Items]                    
Ownership percentage by parent in certain operating assets and cash 100.00%             100.00%    
Unremitted earnings reversed $ 55,000                  
Sale of ownership interest               49.00%    
Minimum [Member]                    
Income Tax Disclosure [Line Items]                    
Income tax examination period       3 years            
Maximum [Member]                    
Income Tax Disclosure [Line Items]                    
Effective income tax rate       35.00%            
Income tax examination period       7 years            
Domestic Tax Authority [Member]                    
Income Tax Disclosure [Line Items]                    
Federal net operating loss carryforwards expiry, beginning year       2033            
Research and development tax credit carryforwards       $ 11,711,000            
Net operating loss carryforwards       $ 18,351,000            
Certain States [Member]                    
Income Tax Disclosure [Line Items]                    
Federal net operating loss carryforwards expiry, beginning year       2018            
Federal net operating loss carryforwards expiry, ending year       2037            
Research and development tax credit carryforwards       $ 11,714,000            
Net operating loss carryforwards       $ 28,770,000