Note receivable (Details)	Dec. 31, 2019 USD ($)
Note receivable [Abstract]
Interest rate	4.50%
Allowance for loan losses	$ 0
Unamortized deferred loan fees and unearned discounts	$ 0

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Name:	us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant