Quarterly report pursuant to Section 13 or 15(d)

Leases - Schedule of Balance Sheets Classification of Leases (Detail)

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Leases - Schedule of Balance Sheets Classification of Leases (Detail) - USD ($)
$ in Thousands
Sep. 30, 2019
Jan. 31, 2019
Jan. 01, 2019
Dec. 31, 2018
Operating leases        
Operating lease right-of-use assets, non-current $ 10,397 $ 7,200 $ 4,180 $ 0
Operating lease liabilities, current 963   976  
Operating lease liabilities, non-current 10,573   $ 3,729 $ 0
Total operating lease liabilities 11,536 $ 7,200    
Finance leases        
Property and equipment, at cost 77      
Accumulated depreciation 39      
Property and equipment, net $ 38      
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List] us-gaap:PropertyPlantAndEquipmentNet      
Finance lease liabilities, current $ 25      
Finance Lease Liability Current Statement Of Financial Position Extensible List us-gaap:OtherLiabilitiesCurrent      
Finance lease liabilities, non-current $ 3      
Finance Lease Liability Noncurrent Statement Of Financial Position Extensible List us-gaap:OtherLiabilitiesNoncurrent      
Total finance lease liabilities $ 28