Annual report pursuant to Section 13 and 15(d)

Income Taxes - Additional Information (Detail)

v3.6.0.2
Income Taxes - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Income Tax [Line Items]    
Provision for income taxes $ 0 $ 0
Net valuation allowance change $ 9,700,000 $ 9,800,000
Cumulative change in ownership 50.00%  
Cumulative change in ownership period 3 years  
Significant change to its unrecognized tax benefits over the next twelve months $ 0  
Income tax examination years The tax years 1998 through 2016 remain open to examination by the major taxing authorities.  
Domestic Tax Authority [Member]    
Income Tax [Line Items]    
Net operating loss carryforward $ 229,100,000  
Research and development tax credit carry forwards $ 7,700,000  
Domestic Tax Authority [Member] | Minimum [Member]    
Income Tax [Line Items]    
NOL carry forward expiry date 2024  
Domestic Tax Authority [Member] | Maximum [Member]    
Income Tax [Line Items]    
NOL carry forward expiry date 2036  
State and Local Jurisdiction [Member]    
Income Tax [Line Items]    
Net operating loss carryforward $ 175,100,000  
Research and development tax credit carry forwards $ 6,300,000  
State and Local Jurisdiction [Member] | Minimum [Member]    
Income Tax [Line Items]    
NOL carry forward expiry date 2017  
State and Local Jurisdiction [Member] | Maximum [Member]    
Income Tax [Line Items]    
NOL carry forward expiry date 2036