Retirement Benefit Plans (Schedule of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4	$ 3
Interest cost	689	819
Expected return on plan assets	(1,452)	(1,273)
Amortization of net loss	508	542
Amortization of net (gain)/loss	(508)	(542)
Net periodic benefit cost	(251)	91
Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	305	240
Interest cost	236	298
Amortization of prior service cost	317	318
Amortization of net loss	158	0
Amortization of net (gain)/loss	(158)	0
Recognition of settlement	188	0
Net periodic benefit cost	$ 1,204	$ 856