Mortgage banking activities (Schedule of Serving Assets at Fair Value) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Servicing Asset at Fair Value, Amount [Roll Forward]
Balance at beginning of year	$ 2,186	$ 2,248
Additions	885	631
Amortization	(723)	(693)	$ (669)
Balances at end of year	$ 2,348	$ 2,186	$ 2,248