Fair value estimates - Schedule of Assets and Liabilities Measured at Fair Value on Nonrecurring Basis (Details) - Nonrecurring Basis - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Impaired loans	$ 5,266	$ 4,944
Other real estate owned	682	878
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Impaired loans	5,266	4,944
Other real estate owned	$ 682	$ 878