Other comprehensive income (loss) - Other Comprehensive Income (Loss) and Related Tax Effects (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Other comprehensive income (loss)
Unrealized gain (loss) on investment securities available-for-sale	$ 273	$ 995
Net gain on the sale of investment securities available-for-sale(1)		(242)
Other comprehensive income gain (loss) before taxes	273	753
Income tax	96	264
Other comprehensive income, net of income taxes	$ 177	$ 489

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Amount before tax, after reclassification adjustments of other comprehensive income (loss).

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount before tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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