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Nature of Organization and Operations - Additional Information (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
3 Months Ended
Jan. 13, 2020
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2019
Nature Of Organization And Operations [Line Items]        
Proceeds from follow-on public offering after deducting underwriting discounts and commissions   $ 381,593 $ 109,927  
Cash and cash equivalents   417,881 $ 288,247 $ 351,985
Marketable securities   $ 228,813    
Follow-on Public Offerings [Member]        
Nature Of Organization And Operations [Line Items]        
Issuance of common stock in follow-on offering, shares 10,925      
Price of common stock $ 37.00      
Proceeds from follow-on public offering after deducting underwriting discounts and commissions $ 381,500      
Underwriting discounts and commissions 22,200      
Offering Cost $ 500      
Over Allotment Option [Member]        
Nature Of Organization And Operations [Line Items]        
Issuance of common stock in follow-on offering, shares 1,425      
Price of common stock $ 37.00