Retirement Benefit Plans (Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1,285	$ 1,710
Expected return on plan assets	(2,435)	(2,778)
Amortization of actuarial (gain) loss	597	422
Amortization of prior service cost	58	58
Settlements	0	873
Net periodic pension (income) expense	(495)	285
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	21	24
Interest cost	52	77
Amortization of actuarial (gain) loss	(1)	8
Amortization of prior service cost	(59)	(80)
Amortization of curtailment	(31)	0
Net periodic pension (income) expense	$ (18)	$ 29