Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies - Additional Information (Detail)

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Commitments and Contingencies - Additional Information (Detail)
1 Months Ended 3 Months Ended 9 Months Ended
Dec. 11, 2017
ft²
Jul. 31, 2018
Sep. 30, 2018
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2018
USD ($)
Sep. 30, 2017
USD ($)
Mar. 01, 2018
USD ($)
Other Commitments [Line Items]              
Expiration of operating lease agreement         2019-01    
Operating lease agreement extended period month and year   2019-01          
Consolidated rent and facilities expense     $ 100,000 $ 100,000 $ 200,000 $ 100,000  
Indemnification obligations     $ 0   0    
Expenses related to indemnification issues         $ 0    
Pike [Member]              
Other Commitments [Line Items]              
Area of office space leased | ft² 3,187            
Lease agreement         On December 11, 2017, we entered into a lease, or the Seattle Lease, with 520 Pike Street, Inc., or Pike, pursuant to which we leased approximately 3,187 square feet located at Suite 2250 at 520 Pike Tower, Seattle, Washington, 98101, which commenced on March 1, 2018. The initial term of the Seattle Lease will expire at the end of the month on the third anniversary of the Seattle Lease.    
Monthly base rent             $ 11,685,000
Monthly base rent, maximum annual increase             12,397,000
Lease, security deposit, annual payment             37,192,000
Lease, security deposit payment, annual decrease             $ 12,397,000
Percentage of profit attributable to lessor     50.00%   50.00%    
Percentage of property if subleased could result in lease termination     50.00%   50.00%