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Net Loss Per Common Share - Additional Information (Detail) - $ / shares
Jun. 30, 2019
Jun. 30, 2018
Convertible Notes due 2020    
Earnings Per Share [Line Items]    
Debt instrument, convertible, conversion price, per share (in dollars per share) $ 94.15  
Convertible Notes due 2018    
Earnings Per Share [Line Items]    
Debt instrument, interest rate, stated percentage, per annum   0.75%