Allowance for Loan and Lease Losses and Unfunded Commitments and Letters of Credit (Changes in the Allowance for Unfunded Commitments and Letters of Credit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance For Loan And Lease Losses And Unfunded Loan Commitments And Letters Of Credit
Beginning balance	$ 2,705	$ 2,930	$ 2,655
Net changes in the allowance for unfunded commitments and letters of credit	425	(225)	275
Ending balance	$ 3,130	$ 2,705	$ 2,930