Capital lease obligation - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Capital Leased Assets [Line Items]
Capital Lease Obligations	$ 3,285
Non-cash capital lease transactions	1,776	$ 2,051	$ 0
Equipment [Member]
Capital Leased Assets [Line Items]
Capitalized cost	3,825
Capital lease, accumulated depreciation	598
Capital lease, depreciation recognized	$ 503

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Amount of increase in lease obligation from new lease.

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Amount before accumulated depreciation of leased physical assets used in the normal conduct of business to produce goods and services.

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The total charge for the use of long-lived depreciable assets subject to a lease meeting the criteria for capitalization.

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The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

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