Pension and Supplemental Executive Retirement Plans - Defined Benefit Plan Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	May 31, 2014
Weighted average assumptions used to determine the benefit obligation
Discount rate used to re-measure pension obligation			4.46%
Components of net periodic pension cost
Service cost	$ 0	$ 0
Interest cost	88	90
Expected return on plan assets	(93)	(86)
Amortization of net actuarial loss	77	60
Amortization of prior service costs	0	0
Net periodic pension cost	72	64
Contributions Paid	$ 79	$ 58