Retirement Benefit Plans (Weighted Average Asset Allocations) (Details) - Pension Plan	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Asset allocations as a percentage of plan assets	100.00%	100.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Asset allocations as a percentage of plan assets	56.00%	56.00%
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Asset allocations as a percentage of plan assets	38.00%	37.00%
Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Asset allocations as a percentage of plan assets	2.00%	2.00%
Other
Defined Benefit Plan Disclosure [Line Items]
Asset allocations as a percentage of plan assets	4.00%	5.00%