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Stock-Based Compensation - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]        
Stock-based compensation expense $ 2,219 $ 2,735 $ 6,969 $ 13,128
Former Chief Financial Officer [Member]        
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]        
Stock-based compensation expense     $ 800  
Former Chief Executive Officer [Member]        
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]        
Stock-based compensation expense       $ 4,100