Retirement Benefit Plans (Weighted Average Assumptions used to Determine Benefit Obligations) (Details)	Dec. 31, 2020	Dec. 31, 2019
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	2.29%	3.07%
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	1.91%	2.82%
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	1.40%	2.50%