Income Taxes - Additional Information (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 15, 2015
Operating Loss Carryforwards [Line Items]      
Increase (decrease) in valuation allowance $ 15.6 $ 7.6  
Net operating loss carryforwards expiration year 2035 2034  
Internal Revenue Service (IRS) [Member] | Earliest Tax Year [Member]      
Operating Loss Carryforwards [Line Items]      
Tax year open to examination 2006    
Internal Revenue Service (IRS) [Member] | Latest Tax Year [Member]      
Operating Loss Carryforwards [Line Items]      
Tax year open to examination 2014    
Federal [Member]      
Operating Loss Carryforwards [Line Items]      
Net operating loss carryforwards   $ 77.3 $ 93.7
Federal [Member] | Research [Member]      
Operating Loss Carryforwards [Line Items]      
Research and development credit carryforwards   $ 1.2 1.4
Research and development tax credit carryforwards expiration year 2035 2034  
State [Member]      
Operating Loss Carryforwards [Line Items]      
Net operating loss carryforwards   $ 58.1 74.1
State [Member] | Research [Member]      
Operating Loss Carryforwards [Line Items]      
Research and development credit carryforwards   $ 0.8 $ 0.9
Research and development tax credit carryforwards expiration year 2030 2029