Retirement Benefit Plans (Weighted Average Assumptions used to Determine Net Periodic Benefit Cost) (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Expected long-term return on assets (as a percent)		5.75%
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	4.12%		3.50%	4.01%
Expected long-term return on assets (as a percent)		6.00%	6.00%	6.50%
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	3.95%		3.30%	3.63%
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)		3.69%	3.00%	3.27%
Assumed healthcare cost trend (as a percent)	6.50%	6.50%	7.00%	7.50%