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Net Loss Per Common Share - Additional Information (Detail) - $ / shares
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Convertible Notes due 2018 and due 2020      
Earnings Per Share [Line Items]      
Debt instrument, convertible, conversion price, per share $ 94.15 $ 94.15 $ 94.15