Loans Receivable - Age analysis of past due loans and leases (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Age Analysis of Past Due Loans and Leases
Total past due	$ 1,046	$ 809
Current	859,110	835,047
Total Accruing Loans and leases	860,156	835,856
Nonaccrual loans and leases	3,831	3,931
Loans and Leases Receivable, Gross, Total	$ 863,987	$ 839,787
Delinquency percentage	0.56%	0.56%
Loans at fair value	$ 12,751	$ 11,422
Commercial mortgage
Age Analysis of Past Due Loans and Leases
Current	324,620	324,169
Total Accruing Loans and leases	324,620	324,169
Nonaccrual loans and leases	1,223	1,224
Loans and Leases Receivable, Gross, Total	$ 325,843	$ 325,393
Delinquency percentage	0.38%	0.38%
Home equity lines and loans
Age Analysis of Past Due Loans and Leases
Total past due	$ 596	$ 348
Current	81,262	81,855
Total Accruing Loans and leases	81,858	82,203
Nonaccrual loans and leases	81	83
Loans and Leases Receivable, Gross, Total	$ 81,939	$ 82,286
Delinquency percentage	0.83%	0.52%
Residential mortgage
Age Analysis of Past Due Loans and Leases
Total past due		$ 195
Current	$ 55,575	51,018
Total Accruing Loans and leases	55,575	51,213
Nonaccrual loans and leases	2,029	2,147
Loans and Leases Receivable, Gross, Total	$ 57,604	$ 53,360
Delinquency percentage	3.52%	4.39%
Construction
Age Analysis of Past Due Loans and Leases
Total past due	$ 253
Current	127,383	$ 116,906
Total Accruing Loans and leases	127,636	116,906
Nonaccrual loans and leases	27
Loans and Leases Receivable, Gross, Total	$ 127,663	116,906
Delinquency percentage	0.22%
Commercial and industrial
Age Analysis of Past Due Loans and Leases
Total past due	$ 186	217
Current	268,371	259,112
Total Accruing Loans and leases	268,557	259,329
Nonaccrual loans and leases	471	477
Loans and Leases Receivable, Gross, Total	$ 269,028	$ 259,806
Delinquency percentage	0.24%	0.27%
Consumer
Age Analysis of Past Due Loans and Leases
Current	$ 751	$ 701
Total Accruing Loans and leases	751	701
Loans and Leases Receivable, Gross, Total	751	701
Leases, net
Age Analysis of Past Due Loans and Leases
Total past due	11	49
Current	1,148	1,286
Total Accruing Loans and leases	1,159	1,335
Loans and Leases Receivable, Gross, Total	$ 1,159	$ 1,335
Delinquency percentage	0.95%	3.67%
Real estate loans
Age Analysis of Past Due Loans and Leases
Loans and Leases Receivable, Gross, Total	$ 593,049	$ 577,945
Loans at fair value	12,751	11,422
Real estate loans | Commercial mortgage
Age Analysis of Past Due Loans and Leases
Loans and Leases Receivable, Gross, Total	325,843	325,393
Real estate loans | Home equity lines and loans
Age Analysis of Past Due Loans and Leases
Loans and Leases Receivable, Gross, Total	81,939	82,286
Real estate loans | Residential mortgage
Age Analysis of Past Due Loans and Leases
Loans and Leases Receivable, Gross, Total	57,604	53,360
Loans at fair value	12,751	11,422
Real estate loans | Construction
Age Analysis of Past Due Loans and Leases
Loans and Leases Receivable, Gross, Total	127,663	116,906
Current | Real estate loans
Age Analysis of Past Due Loans and Leases
Loans at fair value	11,581	(10,098)
30-89 days past due
Age Analysis of Past Due Loans and Leases
Total past due	1,046	809
30-89 days past due | Home equity lines and loans
Age Analysis of Past Due Loans and Leases
Total past due	596	348
30-89 days past due | Residential mortgage
Age Analysis of Past Due Loans and Leases
Total past due		195
30-89 days past due | Construction
Age Analysis of Past Due Loans and Leases
Total past due	253
30-89 days past due | Commercial and industrial
Age Analysis of Past Due Loans and Leases
Total past due	186	217
30-89 days past due | Leases, net
Age Analysis of Past Due Loans and Leases
Total past due	11	49
30-89 days past due | Real estate loans
Age Analysis of Past Due Loans and Leases
Loans at fair value	0	187
Nonaccrual | Real estate loans
Age Analysis of Past Due Loans and Leases
Loans at fair value	$ 1,170	$ 1,137