Retirement Plans SERP (Details) - Supplemental Employee Retirement Plans, Defined Benefit - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Annual Benefit Amount	$ 50,000
Year of Benefit	20 years
Defined Benefit Plan, Other Information-Number of Employees Covered	2
Defined Benefit Plan, Other Costs	$ 40,000	$ 43,000	$ 29,000
Pension and Other Postretirement Defined Benefit Plans, Liabilities	$ 597,000	$ 658,000