Lease liabilities - Schedule of Components of Lease Expense (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Finance lease cost
Amortization of right-of-use asset	$ 19
Interest on lease liabilities
Operating lease cost	197
Short-term Lease, Cost	105
Variable lease cost	181
Total net lease cost	$ 502
Weighted average remaining lease term—finance leases	3 years 3 months 29 days
Weighted average remaining lease term—operating leases	1 year 9 months 29 days
Weighted average discount rate—finance leases	7.11%
Weighted average discount rate—operating leases	5.37%