Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
$ in Thousands
9 Months Ended
Jan. 01, 2019
Sep. 30, 2019
Sep. 30, 2018
Significant Accounting Policies [Line Items]      
Additional operating lease assets   $ (238) $ 0
Additional operating lease liabilities   $ (487) $ 0
Accounting Standards Update 2016-02      
Significant Accounting Policies [Line Items]      
Additional operating lease assets $ 14,300    
Additional operating lease liabilities 15,300    
De-recognition of build-to-suit asset and corresponding lease obligation 10,300    
Cumulative effect adjustment to opening balance of accumulated deficit, expected decrease $ 400