Commitments and Contingent Liabilities (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Contingencies And Commitments [Line Items]
Mortgage loans in the process of origination	$ 3.6	$ 4.4
Mortgages loan held for sale	$ 4.6	$ 4.1
Minimum
Contingencies And Commitments [Line Items]
Mortgage loans in the process of origination, funding period	60 days
Maximum
Contingencies And Commitments [Line Items]
Mortgage loans in the process of origination, funding period	90 days