XML 91 R77.htm IDEA: XBRL DOCUMENT v3.10.0.1
Income Taxes - Additional Information (Detail) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2016
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Mar. 30, 2016
Dec. 31, 2015
Income Tax Disclosure [Line Items]            
Effective income tax rate   21.00% 34.00% 34.00%    
Tax benefit recognized     $ 0 $ 0    
AMT credit carryforwards   $ 736,000        
Provisional tax benefit due to new Tax Act   122,000        
Untaxed accumulated unremitted foreign earnings   813,000        
Valuation allowance, deferred tax assets   30,031,000 33,024,000      
Research and development tax credit carryforwards   23,244,000 20,019,000      
Accrued interest   1,462,000 1,104,000 946,000   $ 830,000
Net interest expense   7,000 6,000 $ 6,000    
Potential payment of interest   $ 35,000 $ 29,000      
Converpower Corporation [Member]            
Income Tax Disclosure [Line Items]            
Ownership percentage by parent in certain operating assets and cash         100.00%  
Unremitted earnings reversed $ 55,000          
Maximum [Member]            
Income Tax Disclosure [Line Items]            
Effective income tax rate     35.00%      
Domestic Tax Authority [Member]            
Income Tax Disclosure [Line Items]            
Federal net operating loss carryforwards expiry, beginning year   2033        
Research and development tax credit carryforwards   $ 12,139,000        
Net operating loss carryforwards   $ 2,584,000        
Certain States [Member]            
Income Tax Disclosure [Line Items]            
Federal net operating loss carryforwards expiry, beginning year   2019        
Federal net operating loss carryforwards expiry, ending year   2037        
Research and development tax credit carryforwards   $ 14,920,000        
Net operating loss carryforwards   $ 8,249,000