Long-term debt - Fixed and adjustable rate information (Details) $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)
Debt Instrument
Number of FHLB advances entered \| item	2
FHLB long-term advances \| $	$ 16,000	$ 0
FHLB advance one
Debt Instrument
FHLB advances term	1 year
FHLB advance two
Debt Instrument
FHLB advances term	2 years

Amount of advances from the Federal Home Loan Bank (FHLB).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

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