Lease liabilities - Schedule of Components of Lease Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Finance lease cost
Amortization of right-of-use assets	$ 12
Operating lease cost	528	$ 31
Short term lease cost	28
Variable lease cost	74	48
Total net lease cost	$ 642	$ 79
Weighted average remaining lease term – finance leases	3 years 1 month 13 days	1 year 5 months 1 day
Weighted average remaining lease term – operating leases	8 years 1 month 9 days	2 years 6 months 29 days
Weighted average discount rate – finance leases	7.11%	6.94%
Weighted average discount rate – operating leases	12.63%	6.00%

Amount of amortization expense attributable to right-of-use asset from finance lease.

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Weighted average discount rate for finance lease calculated at point in time.

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Weighted average remaining lease term for finance lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of lease cost recognized by lessee for lease contract.

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Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

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Weighted average discount rate for operating lease calculated at point in time.

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Weighted average remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of short-term lease cost, excluding expense for lease with term of one month or less.

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Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases.

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