Loans and allowance for loan losses (Schedule of loans by risk rating and portfolio segment) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	$ 757,098	$ 677,006	$ 651,046
Pass
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	742,962	660,090
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	4,235	7,805
Substandard
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	5,448	6,163
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	4,453	2,948
Indirect
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	354,394	297,144	272,892
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	245,704	223,030	224,699
Commercial real estate | Undisbursed construction loans
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	16,654	12,870
Commercial real estate | Undisbursed construction loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	16,654	12,870
Commercial real estate | Undisbursed construction loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Commercial real estate | Undisbursed construction loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Commercial real estate | Undisbursed construction loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Commercial real estate | Non-residential
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	208,778	197,499
Commercial real estate | Non-residential | Pass
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	200,820	186,020
Commercial real estate | Non-residential | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	3,614	6,840
Commercial real estate | Non-residential | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	4,175	4,639
Commercial real estate | Non-residential | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	169	0
Commercial real estate | Multifamily
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	20,272	12,661
Commercial real estate | Multifamily | Pass
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	19,888	12,261
Commercial real estate | Multifamily | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Commercial real estate | Multifamily | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	384	400
Commercial real estate | Multifamily | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	41,344	43,534	44,387
Residential real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	38,687	41,249
Residential real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Residential real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Residential real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	2,657	2,285
Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	88,187	83,203	79,055
Commercial and industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	86,255	81,111
Commercial and industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	621	965
Commercial and industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	889	1,124
Commercial and industrial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	422	3
Consumer
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	27,469	30,095	$ 30,013
Consumer | Indirect
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	354,394	297,144
Consumer | Indirect | Pass
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	353,720	296,692
Consumer | Indirect | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Consumer | Indirect | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Consumer | Indirect | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	674	452
Consumer | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	17,336	19,269
Consumer | Home equity | Pass
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	16,854	19,071
Consumer | Home equity | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Consumer | Home equity | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Consumer | Home equity | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	482	198
Consumer | Other consumer
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	10,133	10,826
Consumer | Other consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	10,084	10,816
Consumer | Other consumer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Consumer | Other consumer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Consumer | Other consumer | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	$ 49	$ 10