Employee Benefit Plans, Defined Contribution Plan, Deferred Compensation and Other (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) Employee	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Defined Contribution Plan [Abstract]
Maximum elective employee contribution percentage	15.00%
Company matching contribution percentage	100.00%
Maximum annual Company contribution for each employee	$ 2,800
Maximum annual Company contribution as a percentage of employee's compensation	4.00%
Annual Company discretionary contribution	$ 1,200
Number of employees participating in enhanced feature of plan | Employee	30
Contributions to defined contribution plan	$ 266,000	$ 261,000	$ 262,000
Deferred Compensation [Abstract]
Present value of future obligations	3,981,000	3,894,000
Total cash value of insurance policies	3,152,000	2,830,000
Net expenses under deferred compensation plans	252,000	557,000	380,000
Other [Abstract]
Amount payable upon retiree's death	2,000
Present value of future obligations	120,000	103,000
(Income) expenses under retiree life insurance program	$ 19,000	$ 9,000	$ (4,000)