Mortgage Servicing Rights (Sensitivity analysis) (Details 5) - Mortgage Servicing Rights - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Constant Prepayment Rate
Decrease in fair value from 25 basis points ("bps") adverse change	$ (332)	$ (321)
Decrease in fair value from 50 bps adverse change	(657)	(636)
Discount Rate
Decrease in fair value from 25 bps adverse change	(289)	(288)
Decrease in fair value from 50 bps adverse change	$ (572)	$ (570)