Retirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Retirement Benefits [Abstract]
Automatic Annual Contribution Employees Hired Before January 1, 2009 Benefit Reduction Under Certain Amendments Minimum, percent			5.00%
Automatic Annual Contribution Employees Hired Before January 1, 2009 Due Benefit Reduction Under Certain Amendments Maximum, percent			7.00%
Employer's matching contribution to 401(k) of employees hired on or after January 1, 2009, percent			50.00%
Maximum annual contribution per employee, percent			3.00%
Funding and administrative costs of noncontributory defined benefit retirement plan and 401(k) plan [Abstract]
401(k) plan	$ 119	$ 102	$ 336	$ 298
Qualified noncontributory defined benefit retirement plan [Member]
Funding and administrative costs of noncontributory defined benefit retirement plan and 401(k) plan [Abstract]
Qualified noncontributory defined benefit retirement plan	279	267	804	789
Components of net periodic pension cost [Abstract]
Service cost	0	0	0	0
Interest cost	17	17	51	51
Amortization of unrecognized net loss	4	0	12	0
Net periodic pension cost	21	$ 17	63	$ 51
Recognized in accumulated other comprehensive income [Abstract]
Net actuarial (gain) loss	160		160		$ 142
Past service cost	0		0		0
Total recognized, net of tax	$ 160		$ 160		$ 142