Retirement Benefit Plans (Assumptions Used in Accounting for Defined Benefit Plans) (Details) - Pension Plan	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on assets for net periodic benefit cost	7.00%	7.50%
Minimum
Defined Benefit Plan Disclosure [Line Items]
Weighted average discount rates for pension benefit obligation	2.02%	2.98%
Weighted average discount rates for net periodic benefit cost	2.98%	4.10%
Maximum
Defined Benefit Plan Disclosure [Line Items]
Weighted average discount rates for pension benefit obligation	2.36%	3.20%
Weighted average discount rates for net periodic benefit cost	3.20%	4.20%