Loans (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Net unamortized loan origination costs	$ 3,800	$ 3,000
Net unamortized premiums on purchased loans	878	783
Loans pledged as collateral	1,600,000	1,400,000
Residential loans in process of foreclosure	4,400	5,700
Interest lost on nonaccrual loans	1,300	1,600	$ 1,500
Interest income recognized for nonaccrual loans	335	640	$ 522
Nonaccrual loans	$ 11,800	$ 18,600