Allowance for Credit Losses (Recorded Investments in Troubled Debt Restructured Loans) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Pre-modification outstanding recorded investment	$ 1,856	$ 1,783
Post-modification outstanding recorded investment	1,987	1,914
Recorded Investment	1,781	1,857
Residential Mortgage [Member]
Pre-modification outstanding recorded investment	676	603
Post-modification outstanding recorded investment	805	732
Recorded Investment	643	690
Commercial Mortgage [Member]
Pre-modification outstanding recorded investment	992	992
Post-modification outstanding recorded investment	992	992
Recorded Investment	967	982
Consumer: Home Equity [Member]
Pre-modification outstanding recorded investment	148	148
Post-modification outstanding recorded investment	148	148
Recorded Investment	141	146
Consumer: Other [Member]
Pre-modification outstanding recorded investment	40	40
Post-modification outstanding recorded investment	42	42
Recorded Investment	$ 30	$ 39