Loan Servicing (Unpaid Principal Balances of Loans Serviced) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Servicing Assets at Fair Value [Line Items]
Unpaid principle balance of loans serviced	$ 336,237	$ 320,790
Freddie Mac
Servicing Assets at Fair Value [Line Items]
Unpaid principle balance of loans serviced	320,334	301,263
Fannie Mae
Servicing Assets at Fair Value [Line Items]
Unpaid principle balance of loans serviced	5,249	7,355
Federal Home Loan Bank
Servicing Assets at Fair Value [Line Items]
Unpaid principle balance of loans serviced	9,313	10,621
Other investors
Servicing Assets at Fair Value [Line Items]
Unpaid principle balance of loans serviced	$ 1,341	$ 1,551