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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
$ in Thousands
1 Months Ended 9 Months Ended
Jul. 31, 2017
Sep. 30, 2019
Jan. 01, 2019
Accounting Policies [Abstract]      
Lease, practical expedients, package   true  
Lessee, operating lease, existence of option to extend true true  
Lessee, operating lease, option to extend   options to extend the lease when it is reasonably certain that option will be exercised  
Operating lease, right-of-use asset   $ 17,674 $ 15,900
Operating lease, lease liability   $ 25,310 $ 24,000