Commitments and Contingent Liabilities (Allowance for Losses on Mortgage Loans Sold) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Balance at beginning of year	$ 1,029	$ 1,029
Provision charged to operating expense	0	0
Recoveries	0	0
Charge-offs	(76)	0
Balance at end of year	$ 953	$ 1,029