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, 2019	Dec. 31, 2018	Dec. 31, 2017
Assumptions (end of period):
Discount rate used in determining benefit obligation	2.98%	4.05%
Reconciliation of funded status (end of period):
Accumulated benefit obligation	$ (12,376)	$ (11,687)
Projected benefit obligation	(12,376)	(11,687)
Fair value of plan assets	10,988	9,669
Funded status	(1,388)	(2,018)
Net actuarial loss	(4,010)	(4,130)
Accumulated other comprehensive loss	(4,010)	(4,130)
Prepaid pension cost	2,622	2,112
Net amount recognized as of December 31	(1,388)	(2,018)
Changes in projected benefit obligation:
Benefit obligation as of beginning of period	11,687	12,758
Interest cost	454	424
Actuarial liability loss (gain)	1,083	(628)
Benefits paid	(848)	(867)
Benefit obligation as of end of period	12,376	11,687	$ 12,758
Change in plan assets:
Fair value of plan assets as of beginning of period	9,669	11,153
Actual return on plan assets (net of expenses)	1,667	(617)
Employer contributions	500
Benefits Paid	(848)	(867)
Fair value of plan assets as of end of period	10,988	9,669	11,153
Net periodic pension cost:
Service cost - benefits earned during the period
Interest cost on projected benefit obligation	454	424
Expected return on plan assets	(607)	(694)
Recognized actuarial loss	143	106
Net periodic pension cost	$ (10)	$ (164)
Discount rate	4.05%	3.45%
Expected return on plan assets	6.50%	6.50%	6.50%