Stock Compensation Plans (Stock Purchase Plan) (Details) - Stock Purchase Plan - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Stock purchase plan
Purchase price of shares in terms compared to market price per share (as a percent)	90.00%
Annual purchase limitation per employee	$ 22,500
Compensation expense	$ 0
Common stock, shares authorized (in shares)	2,000,000
Shares sold to employees (in shares)	51,541	45,343
Value of shares sold to employees under purchase plan	$ 2,800,000	$ 2,300,000
Shares available (in shares)	475,146