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Employee Stock Purchase Plan - Additional Information (Detail) - USD ($)
12 Months Ended
Nov. 14, 2016
May 13, 2016
Nov. 14, 2015
May 14, 2015
Feb. 27, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Purchase price granted           $ 7.53    
Employee [Member] | 2014 Employee Stock Purchase Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Share-based compensation arrangement by share-based payment award, shares issued in period         300,000 58,702 16,422 8,394
Purchase price granted $ 3.32 $ 2.95 $ 9.30 $ 19.29       $ 9.88
Exercise price for awards granted as percentage of market value on the date of grant         85.00% 85.00% 85.00% 85.00%
Stock-based compensation expense           $ 158,000 $ 156,000 $ 46,000