Investment securities (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Available-For-Sale and Held-to-Maturity Securities Table [Line Items]
Investment securities available-for-sale	$ 310,262	$ 319,882
Available-for-sale securities pledged as collateral	118,000	187,300
Proceeds from Sale and Maturity of Marketable Securities	30,000	63,500
Proceeds from sale of available-for-sale securities			$ 400
Private Label Mortgage Backed Securities
Schedule Of Available-For-Sale and Held-to-Maturity Securities Table [Line Items]
Investment securities available-for-sale	$ 7,800	$ 9,300