Retirement Benefit Plans (Other Changes in Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income) (Details) - Other Postretirement Benefits Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Current year actuarial loss	$ 194	$ 46
Amortization of actuarial gain (loss)	1	(8)
Amortization of prior service credit	59	80
Amortization of curtailment	31	0
Transfers	46	0
Total recognized in other comprehensive loss (income)	$ 331	$ 118