Leases - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2016	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019
Loss Contingencies [Line Items]
Operating lease right-of-use asset		$ 716		$ 800
Operating lease liability		$ 757		$ 700
Rent expense			$ 100
Weighted-average remaining lease term, operating leases (Year)		3 years 10 months 24 days
Weighted-average discount rate, Operating leases		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