Fair value measurement (Narrative) (Details)	3 Months Ended	9 Months Ended
Sep. 30, 2020 USD ($) swap	Sep. 30, 2020 USD ($) swap	Sep. 30, 2019 USD ($)
Interest Rate
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Number of interest rate swaps \| swap	1	1
Notional amount	$ 4,700,000	$ 4,700,000
Fair value	500,000	500,000
Warrant
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Warrants issued	$ 0	$ 0	$ 0

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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- Definition

Nominal or face amount used to calculate payment on derivative.

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- Definition

The number of derivative instruments of a particular group held by the entity.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of issuances of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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