Leases - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	6 Months Ended
	Jan. 31, 2016	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019
Loss Contingencies [Line Items]
Operating lease right-of-use asset			$ 671		$ 800
Operating lease liability			$ 717		$ 700
Rent expense		$ 100		$ 200
Weighted-average remaining lease term, operating lease (Year)			3 years 8 months 1 day
Weighted-average discount rate, Operating lease			6.50%
Operating Lease Agreement To Lease Office Space [Member] | San Francisco [Member]
Loss Contingencies [Line Items]
Operating lease agreement expiration date	Apr. 30, 2019
Vancouver Lease [Member] | Vancouver [Member]
Loss Contingencies [Line Items]
Operating lease agreement expiration date			Feb. 28, 2023
Additional lease term to be extended			5 years