Stock Compensation (Schedule of Valuation Assumptions) (Details) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock options expense for the year	$ 209	$ 282	$ 261
Aggregate exercise date intrinsic value of options exercised during the year	$ 5,177	$ 3,416	$ 2,633
Expected life of options in years, based upon historical experience	5 years	5 years	5 years
Risk-free interest rate	1.90%	1.10%	1.40%
Expected volatility, based upon historical volatility	17.50%	15.50%	16.10%
Expected dividend yield	2.80%	2.90%	2.50%
Average estimated value of options granted during the year	$ 14.42	$ 9.05	$ 8.49