Retirement Plans (Changes in Benefit Obligations, Components of Benefit Costs, Weighted-Average Assumptions, and Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assumptions (end of period):
Discount rate used in determining benefit obligation	4.05%	3.45%
Reconciliation of funded status (end of period):
Accumulated benefit obligation	$ (11,687)	$ (12,758)
Projected benefit obligation	(11,687)	(12,758)
Fair value of plan assets	9,669	11,153
Defined benefit plan, funded status of plan, total	(2,018)	(1,605)
Net actuarial loss	(4,130)	(3,554)
Accumulated other comprehensive loss	(4,130)	(3,554)
Prepaid pension cost	2,112	1,949
Net amount recognized as of December 31	(2,018)	(1,605)
Changes in projected benefit obligation:
Benefit obligation as of beginning of period	12,758	12,618
Interest cost	424	471
Actuarial liability (gain)/loss	(628)	554
Benefits paid	(867)	(885)
Benefit obligation as of end of period	11,687	12,758	$ 12,618
Change in plan assets:
Fair value of plan assets as of beginning of period	11,153	10,415
Actual return on plan assets (net of expenses)	(617)	1,623
Benefits Paid	(867)	(885)
Fair value of plan assets as of end of period	9,669	11,153	10,415
Net periodic pension cost:
Service cost - benefits earned during the period
Interest cost on projected benefit obligation	424	471
Expected return on plan assets	(694)	(646)
Recognized actuarial loss	106	126
Net periodic pension cost	$ (164)	$ (49)
Discount rate	3.45%	3.88%
Expected return on plan assets	6.50%	6.50%	6.50%