Bank segment - Allowance for loan commitments (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Allowance for loan commitments:
Beginning balance, prior to adoption of ASU No. 2016-13	$ 1,741
Provision	500
Ending balance	3,800
Home equity line of credit
Allowance for loan commitments:
Beginning balance, prior to adoption of ASU No. 2016-13	392
Provision	0
Ending balance	300
Commercial construction
Allowance for loan commitments:
Beginning balance, prior to adoption of ASU No. 2016-13	931
Provision	515
Ending balance	3,191
Commercial loans
Allowance for loan commitments:
Beginning balance, prior to adoption of ASU No. 2016-13	418
Provision	(15)
Ending balance	309
Impact of ASU No. 2016-13
Allowance for loan commitments:
Beginning balance, prior to adoption of ASU No. 2016-13	1,559
Impact of ASU No. 2016-13 | Home equity line of credit
Allowance for loan commitments:
Beginning balance, prior to adoption of ASU No. 2016-13	(92)
Impact of ASU No. 2016-13 | Commercial construction
Allowance for loan commitments:
Beginning balance, prior to adoption of ASU No. 2016-13	1,745
Impact of ASU No. 2016-13 | Commercial loans
Allowance for loan commitments:
Beginning balance, prior to adoption of ASU No. 2016-13	$ (94)